Pull to Ground
The ECU turns a device on by completing the ground side of the circuit. Also called low-side output or ground trigger.
Trap: The wire may show 12V when off and near 0V when on.
Glossary βLiving EFI field guide prototype
EFI Triage turns confusing tuning language into plain-English cards, diagnostic branches, ECU-specific UI maps, and safe next steps.
Start here
The ECU only knows what the sensors, wiring, calibration, firmware, and software project tell it. A number on the laptop can be an engine problem, a wiring problem, a calibration problem, a dashboard-channel problem, or a process-order problem.
First principle: Verify reality before changing the tune.
Choose your pace
These modes define how much explanation the guide gives you. Early users can read everything in Idle Mode, while experienced users can move faster through checklists, UI paths, log channels, and hard-stop warnings.
For brand-new users. Shows plain-language definitions, glossary links, warnings, diagrams, prerequisite checks, and full procedures before telling you what to change.
For users who know some basics but still want structure. Shows the order of operations, UI paths, log channels, normal ranges, and common traps.
For experienced users moving quickly. Shows the short checklist, pass/fail checks, hard stops, next links, and what not to tune yet.
Minimal hand-holding. Shows direct links to cards, log channels, related procedures, source notes, and advanced caveats. Safety gates still stay visible.
Cards
Cards will expand over time. They are the short explanations behind the guide. As EFI Triage grows, new cards will be grouped by electrical basics, sensors, fuel, ignition, software/UI, boost, datalogging, support electronics, and shop talk. New cards can be added without changing the learning path.
Choose a category above to reveal quick links for that card group.
The ECU turns a device on by completing the ground side of the circuit. Also called low-side output or ground trigger.
Trap: The wire may show 12V when off and near 0V when on.
Glossary βA clean ECU-supplied 5V feed for sensors like TPS, MAP, fuel pressure, and oil pressure.
Trap: One shorted sensor can drag down the whole 5V network.
Test procedure βThe ECUβs clean reference ground for sensor signals. Do not casually treat it like dirty chassis ground.
Trap: Fan or alternator load can make bad grounds look like sensor drift.
Ground trip-ups βA sensor or output cannot tell the truth through a bad connector, loose terminal, bent pin, corrosion, or weak lock tab.
Trap: A connector can look plugged in but still have a pushed-out pin or poor terminal contact.
Trip-Up Library βStable ECU power matters before any tuning decision. Battery, charging, grounds, and voltage drop can affect sensors, injectors, ignition, and logs.
Trap: Side-post battery connections can look fine and still cause voltage drop, ECU resets, and strange sensor behavior.
Trip-Up Library βThrottle Position Sensor. TPS tells the ECU what your foot is doing and affects idle state, throttle movement, accel enrichment, flood clear, and WOT detection.
Trap: Do not calibrate TPS until pedal travel, cable movement, linkage, throttle blade, and the correct sensor application are verified.
TPS guide βManifold Absolute Pressure. MAP tells the ECU engine load by reading absolute pressure in the intake manifold.
Trap: Wrong MAP range, wrong scaling, or a poor shared vacuum source can make the ECU load calculation wrong.
MAP guide βCoolant Temperature. CLT affects warmup enrichment, after-start behavior, fan control, idle behavior, and temperature-based corrections.
Trap: Do not tune cold-start or fan behavior until the coolant temperature reading is believable.
CLT / MAT guide βManifold Air Temperature / Intake Air Temperature. The ECU uses this to understand air temperature and correction behavior.
Trap: High MAT is not automatically wrong. On hot-air or heat-soaked boosted cars, the air may actually be hot.
CLT / MAT guide βThe wideband reports fuel mixture result. It helps show whether the engine is richer or leaner than the target.
Trap: The gauge, ECU input, and datalog must agree before using the reading for VE Analyze, fueling changes, or safety decisions.
Wideband guide βFuel pressure is the delivery assumption behind injector flow and commanded fuel. The tune and injector data must agree with the real pressure.
Trap: Many 3.8L Turbo Buick setups start around 43.5 psi line-off, but final setup depends on the actual system and tune assumptions.
Fuel pressure guide βInjector size, flow rating, fuel pressure assumption, and dead time tell the ECU how much fuel the injector should deliver.
Trap: Wrong injector data can create rich/lean weirdness that people try to hide in the VE table.
Injector data guide βThe delay between commanding an injector open and actual fuel flow. Critical at idle and low pulse width.
Trap: Do not hide wrong dead time by mangling the VE table.
Glossary βFuel pump voltage affects fuel delivery. Low voltage can reduce pump output and make the car act lean under load.
Trap: Do not tune around fuel pressure drop caused by weak wiring, poor grounds, bad relays, or voltage loss.
Trip-Up Library βBase timing is the relationship between ECU-commanded timing and actual crank timing.
Trap: The timing table is fiction until commanded timing matches crank timing with a timing light.
Base timing guide βA misfire is a failed or incomplete burn. It can come from ignition, fuel, mechanical issues, or mixture problems.
Trap: A misfire can put oxygen in the exhaust and make the wideband appear lean even when the fuel table is not the root cause.
Triage Trees βKnock is abnormal combustion. It can be real detonation or false noise depending on sensor, engine, exhaust, and drivetrain conditions.
Trap: Do not dismiss knock as false until fuel, timing, boost, MAT, plugs, and mechanical noise are considered.
Base timing guide βA quick snap of the throttle pedal. Useful for observing transient response, not steady-state VE.
Trap: A lean spike during a stab does not automatically mean βchange the VE table.β
Lean on stab branch βPull fuel means reduce commanded fuel in the active area. It does not always mean blindly lowering VE.
Trap: Before changing VE, check target lambda, trims, warmup, AE, dead time, fuel pressure, and scaling.
Glossary ββNoses overβ means the car starts to pull, then falls flat or stops accelerating like it should.
Trap: It can be fuel delivery, ignition breakup, boost control, airflow restriction, converter/load behavior, or safety limitsβnot just the fuel table.
Triage Trees ββBreaks upβ usually means the engine stumbles, misfires, or becomes unstable under load or RPM.
Trap: Ignition problems often get misread as fueling problems because the wideband can show misleading lean behavior during misfire.
Triage Trees βUniversal Trip-Up Library
EFI Triage tracks recurring garage-level traps across different cars, ECUs, tuning software, and support electronics. These checks are not glamorous, but they prevent people from tuning around mechanical, electrical, or signal problems.
A sensor cannot tell the truth through a bad connector.
Critical engine control should not depend only on a dash, display, or CAN-based support device if the ECM can control it directly.
A bad ground can make good parts look bad.
Unstable power creates fake tuning problems.
The software cannot fix a pedal, cable, or throttle body that does not move correctly.
Triage trees
Before following a symptom branch, check the Universal Trip-Up Library. Many βtuning problemsβ start with connectors, grounds, power, or physical movement issues.
Procedures
Procedures are most useful when they are done in the right order. For the ECUGN / TunerStudio startup sequence, start with the Phase One Index and work top-down unless the earlier checks are already verified.
Do first: Back up tune, verify throttle linkage, verify 5V reference and sensor ground if readings drift.
Pass: stable closed value, smooth sweep, no dropouts, returns to closed, WOT reaches expected full range.
Do not touch yet: Accel enrichment.
Trap: The wideband gauge can be right while the ECU is wrong.
Watch: AFR/lambda, target, EGO correction, battery voltage, fuel type/stoich assumptions.
Hard stop: Do not tune ignition or boost if commanded timing does not match crank timing.
ECU and support electronics
This prototype starts with ECUGN/TunerStudio and DDefi because that stack has real beginner friction: software project layers, channel mapping, dash interpretation, and TunerStudio UI navigation.
Start with the Phase One Index for ECUGN / TunerStudio setup order. If values disagree between the ECU, dash, logger, or gauge, check the Universal Trip-Up Library before blaming the tune.
Use the ECM or a proper hardwired failsafe path for engine-critical control whenever possible. Dash outputs and CAN-based support devices can be useful, but they should not be the only control path for anything that must keep the engine safe.
Glossary + Shop Talk Decoder
Glossary terms explain the language. The Universal Trip-Up Library explains the common real-world problems behind the language. For ECUGN / TunerStudio setup order, use the Phase One Index.
Throttle Position Sensor. TPS tells the ECU what your foot is doing. It is used for idle state, accel enrichment, flood clear, throttle movement rate, and driver intent.
Manifold Absolute Pressure. MAP tells the ECU engine load by measuring absolute pressure in the intake manifold. Key-on engine-off MAP should be close to local barometric pressure.
Coolant Temperature. The ECU uses CLT for warmup enrichment, after-start behavior, fan control, idle behavior, and temperature-based corrections. A cold engine should usually show CLT close to ambient temperature before startup.
Manifold Air Temperature. A temperature reading taken in or near the intake manifold so the ECU can estimate the temperature of the air charge entering the engine. On boosted and hot-air cars, MAT can be much higher than ambient temperature.
Intake Air Temperature. A general air-temperature reading used by the ECU for air-density and temperature correction. Depending on the system, IAT may be measured in the intake tube, charge pipe, air cleaner area, or intake manifold.
Fuel mixture reference where 1.00 means stoichiometric for the fuel being used. Lambda is cleaner than AFR when fuel changes because lambda keeps the target meaning stable across gasoline, E85, alcohol, and blended fuels.
Accel Enrichment. Extra fuel added when throttle or load changes quickly. Do not tune AE until TPS, MAP, wideband scaling, and steady-state fueling are verified.
Wide Open Throttle. The throttle is fully open. WOT tuning should come after sensor truth, fuel pressure, injector data, base timing, warm idle, light-load behavior, and clean logs are verified.
ECU output that turns something on by completing ground. Also called low-side output or ground trigger. Related: relay, fan control, boost solenoid, and other ECU-controlled outputs.
A clean ECU-supplied 5V feed for sensors like TPS, MAP, fuel pressure, and oil pressure. One shorted sensor or damaged wire can drag down the whole 5V network.
The ECUβs clean reference ground for sensor signals. Do not casually treat sensor ground like dirty chassis ground. Bad grounds can make good sensors look bad.
Reduce commanded fuel in the active area. Before changing VE, identify whether the fuel error is from target lambda, trims, warmup, accel enrichment, dead time, fuel pressure, or scaling.
A quick snap of the throttle pedal. Used to observe transient response. Related: TPSdot, MAPdot, accel enrichment, wall wetting, and wideband delay.
The relationship between ECU-commanded timing and actual crank timing. Commanded timing must match crank timing. Verify with fixed timing mode and a timing light before tuning spark, boost, or power.
Injector opening delay. Wrong injector dead time creates rich/lean weirdness especially at idle and low pulse width. Do not hide wrong dead time by mangling the VE table.
Founding Access
EFI Triage is in early development. Founding Access is for people who want early access to the guide, support the project while it is being built, and help shape the first real diagnostic paths.
This is not a finished tuning course, and it is not a replacement for knowing the engine. It is a structured field guide that helps beginners slow down, verify reality, and follow the correct order instead of chasing random forum advice.
To see what is working now and what is being built next, check the Current Build Status. Questions or access issues can go to Support and Feedback.
Join Founding AccessQuestions or access issues? Email support@efitriage.com.
Who this is for
Beginners and intermediate users working through EFI setup, first start, sensor verification, base timing, fuel pressure, idle, cruise, throttle stab, and WOT readiness.
Anyone looking for magic tune numbers, blind VE table changes, or permission to skip mechanical, wiring, sensor, fuel, and timing verification.
The first practical content path is ECUGN and TunerStudio: backup the project, verify sensors, confirm timing, enter injector data, and prove the system before tuning.
Current Build Status
This is the first working version of EFI Triage. The foundation is live: the guide structure, learning modes, glossary, triage trees, ECUGN / TunerStudio starter path, Stripe Founding Access, and support email are all in place.
For the longer build path, see the Roadmap. To support the early build, see Founding Access.
Founding Access is early access to a living guide. You are not buying a finished course yet. You are helping fund and shape the first build while getting access as it develops.
Questions or access issues? Email support@efitriage.com.
Phase One Index
Use this as the quick navigation path. Work from the top down unless you already know the earlier checks are verified.
First deep card
TPS is the throttle position sensor. It tells the ECU where the throttle is. Do not tune around TPS problems. Prove the signal first.
TPS is used for driver intent, idle state, accel enrichment, flood clear, and throttle movement rate. It does not directly measure airflow. It tells the ECU what your foot is doing.
In TunerStudio, TPS must be calibrated so the ECU knows closed throttle and wide-open throttle.
TunerStudio path:
Tools β Calibrate TPS
Basic procedure:
Do not calibrate TPS until the throttle system can physically move correctly. Software cannot fix a pedal, cable, linkage, or throttle blade problem.
On many factory-style Turbo Buick scan-tool setups, closed-throttle TPS is commonly set around 0.42 volts. This is a useful starting reference, not a universal final rule.
On ECUGN / TunerStudio, still use the software calibration procedure. Teach the ECU closed throttle and WOT, then verify the TPS sweep is smooth and repeatable.
The important point is not chasing one magic number. The important point is that closed throttle, WOT, and the sweep are believable every time.
Application note: If replacing the TPS sensor, verify that the sensor is specific to the year and configuration of the car. It makes a difference.
Hot-air Turbo Buick cars do not use the same TPS application as the later 1986β1987 intercooled cars. A hot-air owner who buys the more common 1986β1987 TPS may end up with a sensor that does not fit, sweep, or operate correctly for the application.
Do not tune accel enrichment yet. Do not chase a throttle-stab lean spike yet. Do not blame the VE table yet.
TPS must be calibrated and proven stable before throttle movement tuning means anything.
Do not tune accel enrichment, throttle-stab response, idle state, or VE table behavior until TPS is calibrated, physically verified, and returning consistently.
Second deep card
MAP is manifold absolute pressure. In speed-density tuning, MAP is one of the main ways the ECU knows engine load. If MAP is wrong, the fuel and spark tables are being used in the wrong place.
MAP tells the ECU how much pressure is in the intake manifold. Low MAP usually means vacuum or light load. Higher MAP means more load. MAP above barometric pressure means boost.
On an ECUGN / TunerStudio setup, MAP affects fuel calculation, spark table position, datalogging, boost interpretation, and safety decisions.
The MAP sensor needs a clean manifold vacuum and pressure signal. Do not assume any random vacuum tee is good enough.
Key-on engine-off MAP should be close to local barometric pressure. It does not have to read 101 kPa unless local barometric pressure is actually near 101 kPa.
On modified Turbo Buick setups, verify whether the car is using a 2-bar, 3-bar, or other MAP sensor and make sure the ECU, dash, logger, and any alcohol-control or boost-related system are using the correct signal and scaling.
If the MAP sensor range or scaling is wrong, the ECU may be using the wrong load area. That makes fuel, spark, boost, and logs suspect.
Key on, engine off:
MAP should read close to local barometric pressure.
At higher elevation, it will usually be lower than sea-level 101 kPa. Do not assume 101 kPa is always correct.
At idle, MAP should drop lower because the engine is pulling vacuum.
Do not change VE, spark, boost control, or accel enrichment until MAP is believable.
If MAP is scaled wrong, the ECU may be looking at the wrong load cell. That makes every table decision suspect.
Do not tune VE, spark, boost control, self-tune, or throttle-response behavior until MAP scaling, wiring, and the manifold pressure source are believable.
Third deep card
CLT and MAT are temperature signals. CLT tells the ECU engine coolant temperature. MAT or IAT tells the ECU intake air temperature. If these readings are wrong, startup, warmup, fueling corrections, fan control, and heat-related decisions can all be wrong.
CLT is coolant temperature. The ECU uses it for warmup enrichment, after-start behavior, fan control, idle behavior, safety logic, and temperature-based corrections.
A cold engine should show a CLT value close to ambient temperature before startup.
MAT or IAT is intake air temperature. The ECU uses it for air-density correction and heat-related tuning decisions.
On a hot-air turbo Buick, MAT is not decoration. It is part of the engineβs survival margin.
Before startup, CLT and MAT / IAT should usually read close to ambient temperature if the car has been sitting. They do not need to be identical, but they should be believable for the conditions.
On hot-air and heat-soaked boosted combinations, MAT / IAT can be much higher than ambient. Readings in the 120β180Β°F range can happen depending on heat soak, airflow, boost, sensor location, underhood heat, and intake layout.
A high MAT reading is not automatically a bad sensor or a bad tune. First decide whether the air charge is actually hot, whether the sensor location is heat soaked, or whether the reading is caused by wiring, calibration, or sensor error.
On hot-air Turbo Buick applications, a useful MAT / IAT location may be the front of the intake manifold, near the plugged boss / hex plug area by the CLT sensor. This location can place the sensor closer to the actual air charge entering the engine.
A long-nose MAT / IAT sensor may be preferred so the sensing element reaches into the air stream instead of mainly reading heat-soaked metal.
Verify thread size, sensor depth, sealing, clearance, connector, calibration, and wiring before installation.
A standard / Lo-IAT sensor may be appropriate for manifold MAT on many hot-air Turbo Buick setups because it has good resolution in the range where the engine normally operates. A Hi-IAT sensor may be useful for hotter locations or compressor-outlet-style measurement.
Do not install an IAT sensor just because the thread fits. The ECU calibration must match the exact sensor curve, and the sensor temperature range must match the environment it will see.
Do not tune warmup enrichment, after-start enrichment, MAT correction, or fan behavior until the temperature readings are believable.
Do not use the VE table to hide a cold-start or temperature-sensor problem.
Do not tune warmup enrichment, after-start enrichment, MAT correction, fan control, or cold-start behavior until CLT and MAT / IAT readings are believable.
Fourth deep card
The wideband tells you the fuel result. It does not tell you why the result happened. Before using wideband data to change the tune, prove the gauge, ECU input, calibration curve, fuel display, and log all agree.
A wideband oxygen sensor measures the exhaust oxygen content and reports mixture as AFR or lambda. The ECU can use this for datalogging, closed-loop correction, VE Analyze, and safety review.
A wideband is a truth tool only when it is wired, powered, grounded, calibrated, and interpreted correctly.
Lambda is the cleaner way to think when fuel changes. Lambda 1.00 means stoich for the fuel being used. Richer than stoich is below 1.00. Leaner than stoich is above 1.00.
AFR numbers change with gasoline, E10, E85, methanol, and blended fuels. Lambda keeps the target meaning stable.
Do not use VE Analyze, closed-loop correction, or wideband-based fueling changes until the wideband input is verified.
Do not change the VE table just because the gauge and ECU disagree. First find out which one is wrong.
Fifth deep card
Fuel pressure proves whether the injectors are being fed the pressure the tune assumes. If fuel pressure is wrong, the wideband result may be real, but the cause may not be the VE table.
Injector flow depends on pressure difference across the injector. The tune assumes a certain injector size at a certain base fuel pressure. If actual pressure is different, actual fuel delivery is different.
On a boosted engine, fuel pressure should normally rise with boost when using a boost-referenced regulator.
Key on / pump running:
Confirm base fuel pressure with a gauge before blaming the tune.
Vacuum / boost reference:
Verify the regulator reference line is connected, dry, and seeing true manifold pressure.
Do not tune boost fueling, WOT lambda, or VE table shape until fuel pressure is known and stable.
If pressure drops under load, adding fuel in the table may only hide the real problem until the system runs out of pump or injector.
Sixth deep card
Injector data tells the ECU how much fuel the injectors can deliver and how they behave electrically. If injector size, dead time, fuel pressure, or fuel type assumptions are wrong, the whole fuel model is wrong.
The ECU calculates fuel delivery from engine size, injector size, fuel type, air load, VE, target mixture, and correction tables. Injector data is part of that foundation.
Required Fuel is not the whole tune. It is a base calculation. The VE table works on top of that base.
Do not start shaping the VE table aggressively until injector size, fuel pressure, and basic injector behavior are reasonable.
If injector data is wrong, every fuel correction after it becomes suspicious.
Seventh deep card
Base timing verification proves that the timing commanded by the ECU matches the actual timing at the crank. If commanded timing and crank timing do not agree, the spark table cannot be trusted.
The ECU may command a timing value, but the engine only cares what happens at the crankshaft. A timing light is used to compare commanded timing to actual crank timing.
This must be verified before tuning ignition, boost, knock response, or power.
Do not tune spark advance, boost timing, knock response, or power if base timing is not verified.
If the crank does not match the laptop, the spark table is fiction.
Eighth deep card
First start is not the time to tune for power. First start is for proving the engine runs, the ECU sees believable data, the fuel system is safe, timing is verified, and nothing is leaking, overheating, or lying.
Do not tune boost. Do not tune WOT. Do not chase perfect idle yet. Do not start changing several tables at once.
First start is for proving the basics and finding obvious problems.
Ninth deep card
Warm idle comes before cold-start tuning. Get the engine fully warm, prove the sensors are stable, and make sure the idle system is not fighting the fuel and timing tables.
Warm idle shows whether the engine, throttle position, MAP signal, injector setup, AFR / lambda reading, timing, idle air, and basic VE table are close enough to continue.
If warm idle is unstable, cold start and driveability tuning will be harder and less reliable.
Do not tune cold start yet. Do not tune accel enrichment yet. Do not tune boost yet.
Warm idle is the stable reference point. Fix warm idle before chasing cold-start behavior.
Tenth deep card
The first drive is not for boost or hero pulls. It is for proving that the engine behaves under light load, the sensors stay believable, the wideband result follows the target, and the tune responds predictably.
Do not tune WOT. Do not turn up boost. Do not chase every small transient spike.
First-drive tuning is about light-load confidence and clean data, not maximum power.
Eleventh deep card
A datalog is not one number. Read the event in order. Find what happened, when it happened, what changed first, and which signals can be trusted before changing the tune.
Beginners often stare at AFR / lambda first. That is useful, but it is only the result. Before blaming fuel, check what the engine and ECU were doing at that exact moment.
A lean spot can come from VE, fuel pressure, accel enrichment, injector limit, voltage drop, wrong MAP scaling, wideband delay, or bad sensor data.
Do not change multiple tables from one unclear log. Do not tune from a log with bad sensor data.
One clean log with a clear event is better than ten messy logs with guesses.
ROADMAP
EFI Triage will grow in stages. Founding members help shape which confusing areas get mapped first.
For what is working today, see Current Build Status. To support the early build, see Founding Access. For questions or access issues, use Support and Feedback.
CONTACT
EFI Triage is being built around real confusion points: lingo, UI location, wiring basics, process order, and diagnostic branches.
For the fastest help, include your ECU, tuning software, support electronics, what you have already verified, and the exact symptom. Useful details include whether the issue happens at idle, cruise, throttle stab, first start, warm restart, boost, or WOT.
Send support and founding-member questions to:
This email is active. Better information makes triage faster.
Founding Access supports an early-stage build. EFI Triage is live and useful, but it is not a finished course, complete manual, or one-on-one tuning service yet.
If you joined by mistake or expected a finished product, email support@efitriage.com and the issue will be reviewed fairly.
Full terms, refund policy, and member access details will be expanded as the platform develops.
Paid rollout
Start with a free sample library and a low-cost paid ECUGN / TunerStudio beta. Add AI triage only after the content system is solid.
Sample glossary, intro cards, mission, sample triage.
$0Vendor-specific pathways can be added without locking EFI Triage to one brand. AMP EFI is the first preview pathway.
View AMP EFI previewFull starter guide, ECUGN / TunerStudio cards, checklists, feedback access.
$49/year Join Founding AccessProduct-specific UI maps, PDFs, support-electronics add-ons.
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