Fuel Injector Electrical Circuit Diagnosis
EARLY MODEL VEHICLESNOTE: The following test procedure assumes that the ignition system is functioning, a good spark is present at the plugs, and that the FUEL SYSTEM DIAGNOSIS procedure has been followed to reach this procedure.
NOTE: The fuel system wiring diagrams should be used in conjunction with the following test to correctly diagnose the problem.
Fuel Circuit Diagram:
Connector Identification:
1. Disconnect injectors 1, 2, and 3. Test for continuity between Electronic Control Unit (ECU) 24 pin connector (C517) terminal B1 and ground.
^ If there is continuity go to step 2.
^ If there is no continuity go to step 3.
2. Disconnect connector C104 and check for continuity between C517 terminal B1 and ground.
^ If there is continuity repair short to ground between C517 terminal B1 and C104 pin F7.
^ If there is no continuity repair short to ground between C104 pin F7, C525 pin A, C526 pin A, and/or C527 pin A.
3. Disconnect injectors 4, 5, and 6. Test for continuity between Electronic Control Unit (ECU) 24 pin connector (C517) terminal B2 and ground.
^ If there is continuity go to step 4.
^ If there is no continuity go to step 5.
4. Disconnect connector C104 and check for continuity between C517 terminal B2 and ground.
^ If there is continuity repair short to ground between C517 terminal B2 and C104 pin F8.
^ If there is no continuity repair short to ground between C104 pin F8, C528 pin A, C529 pin A, and/or C530 pin A.
5. If there is no continuity, test injector resistances with an ohmmeter. Injectors should have a resistance of 4-28 ohms.
^ If any injectors have a resistance outside this range, replace the injector(s) and test operation.
^ If all injector resistances are within specifications, the problem is computer related.
LATE MODEL VEHICLES
NOTE: The following test procedure assumes that the ignition system is functioning, a good spark is present at the plugs, and that the FUEL SYSTEM DIAGNOSIS procedure has been followed to reach this procedure.
NOTE: The fuel system wiring diagrams should be used in conjunction with the following test to correctly diagnose the problem.
1. Disconnect all injector connectors and test for continuity between all connector terminals and ground.
^ If there is continuity repair short to ground and test circuit operation.
^ If there is no continuity go to step 2.
2. Measure the resistance across each injector, resistance should be 16 ohms +/- 2 ohms.
^ If the resistance is within specifications go to step 3.
^ Replace any injectors with resistance outside of specifications.
3. Remove the Single Board Engine Controller (SBEC) 60 way connector and inspect for bent or pushed out terminals. Repair or replace any problems before proceeding.
4. Test for continuity between the SBEC 60 way connector, pin 57 (DG/RD wire) and the DG/RD wire of all injectors.
^ If there is continuity go to step 5.
^ Repair open in wiring for any injectors which do not have continuity to the SBEC, pin 57.
5. Test continuity between:
a. Injectors 1 and 4 WT/DB wire and SBEC 60 way connector, pin 16, (WT/DB wire).
b. Injectors 2 and 5 TN wire and SBEC 60 way connector, pin 15, (TN wire).
c. Injectors 3 and 6 YL/WT wire and SBEC 60 way connector, pin 14, (YL/WT wire).
6. Repair any open circuits found and test circuit operation.