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 →Living EFI field guide prototype
Forum advice is not enough. Beginners need the lingo, the UI location, and the correct order.
EFI Triage turns confusing tuning language into plain-English cards, diagnostic branches, ECU-specific UI maps, and safe next steps.
Forum Wizard: “Pull fuel. Check dead time. Verify base timing.”
😵💫
Triage Foreman: “Slow down. What has been verified?”
Start here
The screen is not the engine.
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.
Order of operations
- Back up the tune/project.
- Confirm ECU power during key-on and crank.
- Verify TPS, MAP, CLT, MAT, wideband.
- Enter injector data and fuel pressure assumptions.
- Verify base timing with a timing light.
- First start, warm idle, first drive, then boost.
Choose your pace
Idle, Cruise, Throttle Stab, or WOT.
Idle Mode — explain it all
For brand-new users. Shows plain-language definitions, warnings, diagrams, prerequisite cards, and full procedures.
Cruise Mode — guided checklist
For users who know some basics but still want structure, UI paths, log channels, and reminders.
Throttle Stab Mode — fast triage
For experienced users. Shows the short checklist, pass/fail checks, software location, and danger points.
WOT Mode — pro reference
Minimal hand-holding. Dependency checklist, raw channels, advanced notes, and references. Safety gates still stay visible.
Cards
Short lessons that branch into procedures.
5V Reference
A 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 →Sensor Ground
The ECU’s 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 →TPS
Throttle 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 →MAP
Manifold 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 →Injector Dead Time
The 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 →Base Timing
Commanded 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 →Throttle Stab
A 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 “change the VE table.”
Lean on stab branch →Pull Fuel
Reduce commanded fuel in the active control area. First determine what is actually active.
Question: VE, target lambda, trim, warmup, AE, or fuel pressure?
Decoder →Triage trees
Start from the symptom. Follow the dependency chain.
Lean on throttle stab
- TPS calibrated?
- TPSdot clean?
- MAP response believable?
- Wideband scaling verified?
- Warm steady-state VE close?
- Then tune accel enrichment.
Starts then dies
- ECU stays powered?
- RPM/sync stable?
- Fuel pressure correct?
- MAP believable?
- After-start enrichment active?
- Idle air configured?
DDefi disagrees with TunerStudio
- Is TunerStudio value correct?
- Is DDefi reading the correct channel?
- Is scaling identical?
- Is CAN/serial data live?
- Compare dash, laptop, and log together.
Procedures
Garage-ready steps.
Calibrate TPS — TunerStudio / ECUGN
Fast Triage: Key on, engine off → Tools → Calibrate TPS → capture closed → capture WOT → sweep slowly → verify TPS and TPSdot in log.
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.
Verify Wideband Scaling
Fast Triage: Confirm controller model → match 0–5V curve in ECU → compare gauge vs TunerStudio/log → verify lambda/AFR display convention.
Trap: The wideband gauge can be right while the ECU is wrong.
Watch: AFR/lambda, target, EGO correction, battery voltage, fuel type/stoich assumptions.
Verify Base Timing
Fast Triage: Lock/fix timing → command known value → use timing light → adjust trigger offset if needed → recheck → return to normal timing mode.
Hard stop: Do not tune ignition or boost if commanded timing does not match crank timing.
ECU and support electronics
Choose your ECM. Choose your 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.
Recommended path: ECUGN/TunerStudio + DDefi Dash → verify TunerStudio value first, then map dash channel/scaling.
Glossary + Shop Talk Decoder
Plain meanings with related branches.
Pull to Ground
ECU output that turns something on by completing ground. Related: relay, fan control, boost solenoid, low-side output.
Pull Fuel
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.
Throttle Stab
A quick snap of the throttle pedal. Used to observe transient response. Related: TPSdot, MAPdot, accel enrichment, wall wetting, wideband delay.
Base Timing
The relationship between ECU-commanded timing and actual crank timing. Must be verified with a timing light.
Lambda
Fuel mixture reference where 1.00 means stoichiometric for the fuel being used. Cleaner than AFR when fuel changes.
Dead Time
Injector opening delay. Wrong data creates rich/lean weirdness especially at idle and low pulse width.
Founding Access
Help build the field guide before it becomes polished.
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 AccessWhat you get
- Early access to EFI Triage as the guide develops.
- Plain-English diagnostic cards and procedure branches.
- First access to ECUGN and TunerStudio-focused startup material.
- A way to support the project before it becomes a larger product.
Questions or access issues? Email support@efitriage.com.
Who this is for
Built for the person staring at the laptop, not the person pretending the laptop is the engine.
Good fit
Beginners and intermediate users working through EFI setup, first start, sensor verification, base timing, fuel pressure, idle, cruise, throttle stab, and WOT readiness.
Not a good fit
Anyone looking for magic tune numbers, blind VE table changes, or permission to skip mechanical, wiring, sensor, fuel, and timing verification.
Current focus
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
ECUGN / TunerStudio first-start 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.
1. Back up the project
Save the current tune/project before changing anything. A bad change is easier to fix when there is a known starting point.
2. Verify sensors
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.
3. Confirm timing
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.
4. Enter injector and fuel data
Injector size, dead time, fuel type, fuel pressure, and base assumptions affect the whole tune. Guessing here creates problems everywhere else.
5. First start and warm idle
Start with safe checks: leaks, oil pressure, coolant temperature, idle behavior, charging voltage, AFR sanity, and stable sensor readings.
6. Drive before boost
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 — ECUGN / TunerStudio
TPS is the throttle position sensor. It tells the ECU where the throttle is. Do not tune around TPS problems. Prove the signal first.
What TPS does
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.
Where to find it
TunerStudio path:
Tools → Calibrate TPS
Basic procedure:
- Key on, engine off.
- Throttle fully closed.
- Capture closed throttle.
- Press pedal fully to wide-open throttle.
- Capture WOT.
- Save and test the sweep.
What good looks like
- Closed throttle is stable.
- Throttle sweep is smooth.
- No sudden jumps or dropouts.
- WOT reaches full range.
- TPS returns to the same closed value.
What can fool you
- Bad sensor ground.
- Weak or noisy 5V reference.
- Throttle cable too tight.
- TPS heat drift.
- Wrong gauge or dash channel.
- DDefi dash scaling not matching TunerStudio.
What not to tune yet
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.
Log channels to watch
- TPS
- TPSdot
- RPM
- MAP
- AFR / Lambda
- Accel enrichment, if available
Triage branches
- TPS jumps: check sensor ground, 5V reference, wiring, and sensor condition.
- TPS does not reach full range: recalibrate and check throttle linkage/pedal travel.
- TPS changes as the car warms: check heat drift, grounding, and mechanical throttle movement.
- DDefi disagrees with TunerStudio: check dash channel assignment and scaling.
EFI Triage rule: TPS is not a fuel table. It is a signal. Verify the signal before changing the tune.
Second deep card
MAP — ECUGN / TunerStudio
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.
What MAP does
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.
First sanity check
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.
What good looks like
- Key-on engine-off MAP is close to local barometric pressure.
- Idle MAP drops into a believable vacuum range.
- MAP rises smoothly when throttle opens.
- MAP does not jump, freeze, or flatline.
- Boost readings match the installed MAP sensor range.
What can fool you
- Wrong 2-bar / 3-bar / 4-bar sensor calibration.
- Vacuum hose leak or hose connected to the wrong source.
- Sensor not seeing true manifold pressure.
- Bad sensor ground or 5V reference problem.
- Dashboard showing a different channel than TunerStudio.
- Confusing boost gauge pressure with absolute MAP pressure.
What not to tune yet
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.
Log channels to watch
- MAP
- Baro, if available
- RPM
- TPS
- AFR / Lambda
- Spark advance
- Boost, if shown separately
Triage branches
- MAP reads wrong key-on: check sensor calibration and local barometric pressure.
- MAP does not drop at idle: check vacuum source, hose, engine vacuum, and sensor wiring.
- MAP jumps or drops out: check wiring, sensor ground, 5V reference, and connector condition.
- Boost reading is wrong: confirm MAP sensor range and absolute pressure versus gauge pressure.
EFI Triage rule: MAP tells the ECU where the engine is loaded. If MAP lies, the tune follows the lie.
Third deep card
CLT + MAT / IAT — ECUGN / TunerStudio
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.
What CLT does
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.
What MAT / IAT does
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 engine’s survival margin.
What good looks like
- Cold CLT and MAT are close to ambient temperature.
- CLT rises smoothly as the engine warms.
- MAT responds logically to heat soak and airflow.
- No sudden jumps, flatlines, or impossible values.
- Fan behavior matches the CLT reading and fan settings.
What can fool you
- Wrong thermistor calibration.
- Bad sensor ground or wiring.
- Open circuit reading very cold.
- Shorted sensor or wire reading very hot.
- Air pocket near the coolant sensor.
- MAT heat soak being mistaken for a tuning problem.
What not to tune yet
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.
Log channels to watch
- CLT
- MAT / IAT
- RPM
- MAP
- AFR / Lambda
- Warmup enrichment
- After-start enrichment, if available
- Fan output state, if available
Triage branches
- CLT reads very cold: check unplugged sensor, open circuit, wiring, and calibration.
- CLT reads very hot: check short to ground, wrong calibration, or wiring fault.
- MAT is heat soaked: separate real hot-air behavior from sensor/wiring problems.
- Fan does not act correctly: verify CLT reading before changing fan settings.
EFI Triage rule: Temperature corrections only help if the temperature readings are true.
Fourth deep card
Wideband / Lambda — ECUGN / TunerStudio
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.
What the wideband does
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 vs AFR
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.
What good looks like
- Wideband controller powers up and warms normally.
- Gauge and TunerStudio agree closely.
- Log value matches the live TunerStudio value.
- Reading changes smoothly with fuel and load changes.
- No impossible fixed, pegged, or delayed values.
What can fool you
- Wrong 0–5V calibration curve.
- Analog ground offset.
- Gauge set to AFR while ECU/log is using lambda, or the reverse.
- Fuel type changing the meaning of AFR numbers.
- Exhaust leak near the sensor.
- Sensor not warmed up or sensor aging/failure.
What not to tune yet
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.
Log channels to watch
- AFR / Lambda
- AFR target / Lambda target
- EGO correction
- RPM
- MAP
- TPS
- Pulse width
- Battery voltage
- Fuel pressure, if available
Triage branches
- Gauge and ECU disagree: check 0–5V curve, analog ground, and ECU calibration.
- Reading is stuck rich or lean: check sensor warmup, wiring, controller status, and exhaust leaks.
- Lambda looks right but AFR looks wrong: check fuel stoich and display convention.
- VE Analyze makes ugly changes: verify wideband, target table, injector data, and fuel pressure first.
EFI Triage rule: The wideband shows the result. It does not prove the cause.
ROADMAP
Build path
EFI Triage will grow in stages. Founding members help shape which confusing areas get mapped first.
Now building
- Beginner glossary
- EFI triage cards
- Order of operations
- ECUGN / TunerStudio starter path
- No-start and sensor verification trees
Next
- DDefi dash support map
- AEM wideband setup notes
- Printable worksheets
- First-start checklist
- First-log review guide
Later
- Holley EFI
- HP Tuners
- Haltech
- FuelTech
- AI Triage Assistant
- Printable field guides
CONTACT
Support and feedback
EFI Triage is being built around real confusion points: lingo, UI location, wiring basics, process order, and diagnostic branches.
Need help or found a confusing area?
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.
Refund / early-access note
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
Cheap enough to help, paid enough to build infrastructure.
Start with a free sample library and a low-cost paid ECUGN/TunerStudio beta. Add AI triage only after the content system is solid.
Free
Sample glossary, intro cards, mission, sample triage.
$0Founding Beta
Full starter guide, ECUGN/TunerStudio cards, checklists, feedback access.
$49/yearJoin Founding AccessECU Guide
Product-specific UI maps, PDFs, support-electronics add-ons.
$89/year