Circuit Diagnosis - Fuel Injector

DIAGNOSTIC AIDS
The VCM has integrated circuits that are fault protected; therefore, if a circuit has failed, the integrated circuits may not be damaged. If this is the case, the Ignition Control (IC) will keep the circuit open until you have corrected the fault in the circuit. When you have corrected the fault, reinstall the VCM. Check the circuit. Replace the VCM only if the circuit is still inoperative.

TEST DESCRIPTION
Number(s) below refer to step number(s) on the Diagnostic Table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and stores the freeze frame and failure records data on the scan tool, if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored in the scan tool for later reference.
3. If the no start condition was due to a open fuse, locate and repair any shorts that may have caused the fuse to open before replacement.
4. This step determines if the fuel pump circuit can be controlled by the VCM. The VCM should energize the fuel pump relay and turn the fuel pump ON when commanded by the scan tool. If the engine is not cranking or running, the VCM should de-energize the relay and turn OFF the fuel pump after 2 seconds.
5. Jumping the fuel pump feed terminal to the fuel pump relay ignition feed terminal verifies that the fuel pump relay ignition feed circuit, the fuel pump feed circuit, the fuel pump and fuel ground are all OK.
8. Check for an open ground circuit.
17. Replacement VCMs must be reprogrammed. Refer to the latest Techline information for programming procedures.
18. This step checks the fuel pump ground circuit on the body side of the body harness only. If the fuel pump ground circuit is OK, then the fuel pump feed circuit or the fuel pump ground circuit in the fuel tank harness or the fuel pump itself is malfunctioning.
21. This test will determine if a short to ground on the fuel pump feed circuit caused the fuse to open. To prevent mis-diagnosis, be sure the fuel pump harness is disconnected before the test.before the test.