Diagnostic Aids
Enter this CIRCUIT TEST only when all steps under QUICK TEST have been successfully completed and engine still does not start or if directed here from another test or chart. This test is only intended to diagnose:
- Spark (ECA-controlled).
- Wiring harness circuits (PIP, IGN GND and VPWR).
- ECA.
To prevent replacement of good components, be aware following non-EEC related areas and components may be cause of problem:
- Fuel quality and quantity.
- Ignition (general condition).
- Engine mechanical components.
- Starter and battery circuits.
- Variable reluctance sensor (VRS).
- EDIS module.
- Coil packs.
| Application | Wire Color |
|---|---|
| 1.9L | Red |
| 4.6L | Tan/Yellow |
| Application | Wire Color |
|---|---|
| 1.9L | Light Green/White |
| 4.6L | Pink |
| Application | Wire Color |
|---|---|
| 1.9L | Green/White |
| 4.6L | Gray/Orange |
1) Starting System Ensure fuel pump inertia switch is closed (button pushed in). Try to start engine. If engine does not crank, check vehicle starting and charging systems. If engine cranks, go to next step.
2) Check VREF Signal At TPS Turn ignition off. Disconnect Throttle Position Sensor (TPS). Turn ignition on (engine off). Measure voltage between VREF and SIG RTN at TPS harness connector. See Fig 3 . If voltage is not 4-6 volts, go to CIRCUIT TEST C. If voltage is 4-6 volts, reconnect TPS and go to step 3).
3) Check For Spark At Plugs Disconnect any spark plug wire. Connect spark tester between plug wire and engine ground. Crank engine and check for spark. If spark is present, reconnect spark plug wire and go to step 4). If spark is not present, check ignition system. See EDIS SYSTEM in I - SYS/COMP TESTS article in the ENGINE PERFORMANCE Section.
4) Check IGN GND Continuity Turn ignition off, and wait 10 seconds. Disconnect ECA 60-pin connector, and inspect it for damaged pins, corrosion and loose wires. Repair as necessary. Install Breakout Box (T83L-50-EEC-IV), leaving ECA disconnected. Disconnect EDIS module. Measure resistance between test pin No. 16 at breakout box and IGN GND terminal at EDIS module vehicle harness connector. If resistance is 5 ohms or more, repair open in IGN GND circuit and repeat QUICK TEST . If reading is less than 5 ohms, go to step 5).
5) Check PIP For Short To Power Ensure ignition is turned off. Disconnect EDIS module. Measure voltage between test pin No. 56 at breakout box and negative battery terminal. If voltage is greater than 7 volts, repair PIP circuit short to power. Remove breakout box, and repeat QUICK TEST . If voltage is not greater than 7 volts, go to step 6).
6) Check PIP Circuit Continuity Ensure ignition is turned off. Measure resistance between test pin No. 56 at breakout box and PIP terminal at EDIS module vehicle harness connector. If resistance is less than 5 ohms, go to step 7). If resistance is 5 ohms or more, repair open PIP circuit. Remove breakout box, reconnect all components and repeat QUICK TEST .
7) Check PIP Circuit For Shorts To Ground Ensure ignition is turned off. Measure resistance between test pin No. 56 (PIP) and test pins No. 16, 40, 46 and 60 for short to ground. If any reading is less than 10,000 ohms, repair short in PIP circuit and repeat QUICK TEST . If engine still does not start, go to step 8). If all readings are 10,000 ohms or more, go to step 8).
8) Isolate Shorts In ECA Ensure ignition is turned off. With breakout box installed, connect ECA to breakout box. Disconnect EDIS module. Measure resistance between test pin No. 56 (PIP) and test pins No. 37 and 57 for short to power. Measure resistance between test pin No. 56 and test pins No. 40 and 60 for short to ground. If any resistance is not 20,000-150,000 ohms, replace ECA and repeat QUICK TEST . If all resistances are 20,000-150,000 ohms, go to step 9).
9) Check PIP Signal Turn ignition off. Wait 10 seconds. With breakout box installed, disconnect ECA. Reconnect EDIS module. Measure voltage between test pin No. 56 and test pin No. 16 at breakout box while cranking engine. Record voltage. If voltage is 3-7 volts, go to step 10). If voltage is not 3-7 volts, replace EDIS module and repeat QUICK TEST .
10) Fuel Pump Check Connect pressure gauge to vehicle. Note initial pressure reading. Pressurize fuel system by turning ignition on for one second, and observe pressure gauge. Turn ignition off, and wait 10 seconds. Repeat sequence 5 times. If pressure increases, go to CIRCUIT TEST S. If pressure does not increase, go to FUEL SYSTEM in SYSTEM & COMPONENT TESTING - EEC-IV.