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
For brand-new users. Shows plain-language definitions, warnings, diagrams, prerequisite cards, and full procedures.
For users who know some basics but still want structure, UI paths, log channels, and reminders.
For experienced users. Shows the short checklist, pass/fail checks, software location, and danger points.
Minimal hand-holding. Dependency checklist, raw channels, advanced notes, and references. Safety gates still stay visible.
Cards
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 branch βThrottle position sensor. Used for idle state, accel enrichment, flood clear, and driver intent.
Trap: Do not tune accel enrichment before TPS and TPSdot are verified.
Calibrate TPS βManifold absolute pressure. The main load signal for speed-density tuning.
Trap: Key-on engine-off MAP should match local barometric pressure, not necessarily sea-level 101 kPa.
Verify MAP 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 βCommanded timing must match crank timing. Use fixed timing mode and a timing light.
Rule: If the light disagrees with the laptop, believe the light.
Verify timing 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 βReduce commanded fuel in the active control area. First determine what is actually active.
Question: VE, target lambda, trim, warmup, AE, or fuel pressure?
Decoder βTriage trees
Procedures
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.
Glossary + Shop Talk Decoder
ECU output that turns something on by completing ground. Related: relay, fan control, boost solenoid, low-side output.
Reduce commanded fuel in the active area. Before changing VE, identify whether fuel error is from target lambda, trims, warmup, AE, dead time, pressure, or scaling.
A quick snap of the throttle pedal. Used to observe transient response. Related: TPSdot, MAPdot, accel enrichment, wall wetting, wideband delay.
The relationship between ECU-commanded timing and actual crank timing. Must be verified with a timing light.
Fuel mixture reference where 1.00 means stoichiometric for the fuel being used. Cleaner than AFR when fuel changes.
Injector opening delay. Wrong data creates rich/lean weirdness especially at idle and low pulse width.
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.
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.
First diagnostic path
The first EFI Triage path is built around a simple rule: prove the system before tuning the system. A clean first start begins with file backup, sensor reality, timing verification, injector data, fuel pressure, and safe startup order.
Save the current tune/project before changing anything. A bad change is easier to fix when there is a known starting point.
TPS, MAP, CLT, MAT, wideband, and fuel pressure data must make sense before the tune is blamed. The laptop reports what the system tells it; it does not prove the system is true.
Commanded timing and crank timing must agree. If the timing light disagrees with the laptop, believe the timing light and fix the setup before tuning.
Injector size, dead time, fuel type, fuel pressure, and base assumptions affect the whole tune. Guessing here creates problems everywhere else.
Start with safe checks: leaks, oil pressure, coolant temperature, idle behavior, charging voltage, AFR sanity, and stable sensor readings.
Cruise, throttle stab, and light-load behavior come before WOT. Boost tuning comes after the engine, wiring, sensors, and fuel system have earned trust.
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 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.
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.
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.
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.
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.
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.
ROADMAP
EFI Triage will grow in stages. Founding members help shape which confusing areas get mapped first.
CONTACT
EFI Triage is being built around real confusion points: lingo, UI location, wiring basics, process order, and diagnostic branches.
For now, send feedback, questions, and founding-member support requests to:
support@efitriage.com
This email will be activated shortly. Until then, founding-member communication may be handled manually.
Founding Access supports an early-stage build. If you joined by mistake or expected a finished product, contact support 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.
$0Full starter guide, ECUGN/TunerStudio cards, checklists, feedback access.
$49/yearJoin Founding AccessProduct-specific UI maps, PDFs, support-electronics add-ons.
$89/year