Engine Control Module: Testing and Inspection
Engine Control Module Power Supply Relay, Checking
Special tools, testers and auxiliary items required
• Multimeter.
• Wiring diagram.
Test requirements
• The Engine Control Module (ECM) Power Supply Relay (J271) fuses OK.
• Battery voltage at least 12.5 volts.
• All electrical consumers such as, lights and rear window defroster, switched off.
• Vehicles with automatic transmission, selector lever in position "P" or "N".
• A/C switched off.
• Ground connections between engine/transmission/chassis OK.
• Ignition switched OFF.
Test procedure
- Observe safety precautions. Refer to => [ Safety Precautions ] Safety Precautions
- Observe Clean Working Conditions. Refer to => [ Clean Working Conditions ] Clean Working Conditions
- Perform a preliminary check to verify the customers complaint. Refer to => [ Preliminary Check ] Preliminary Check.
Test sequence
- Remove the Engine Control Module (ECM) Power Supply Relay (J271).
Checking voltage
- Turn the ignition switch ON.
- Using a multimeter, check the Engine Control Module (ECM) Power Supply Relay (J271) socket 30 to ground.
- Switch the ignition OFF.
Specified value: Battery voltage.
If the specified value was not obtained:
- Check the wiring and connections in the power supply circuit to the Engine Control Module (ECM) Power Supply Relay (J271) socket 30 for high resistance, an open or short circuit. Refer to Wiring Diagrams.
- Check the wiring connections for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring connection.
If the specified value was obtained:
- Switch the ignition ON.
- Using a multimeter, check the Engine Control Module (ECM) Power Supply Relay (J271) socket 86 to ground.
- Switch the ignition OFF.
Specified value: Battery voltage.
If the specification was Not obtained:
- Check the wiring from fuse S-15 to relay terminal 86 for an open, high resistance or short circuit to voltage or ground.
- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring connection.
If the specified value was obtained:
Checking wiring
- Remove the Engine Control Module (ECM) Power Supply Relay (J271). Refer to the Repair Information.
- Using a multimeter, check the Engine Control Module (ECM) Power Supply Relay (J271) to the Engine Control Module (ECM) (J623) electrical harness connector T94 for resistance.
Specified value: 1.5 ohms Max.
If the specification was not obtained:
- Check the wiring for an open, high resistance or short circuit to voltage or ground.
- Check the electrical harness connector for damage, corrosion, loose or broken terminals.
- If necessary, repair the faulty wiring connection.
If the specified value was obtained:
- Replace the Engine Control Module (ECM) Power Supply Relay (J271). Refer to the Repair Information.
- Erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.
- Perform a road test to verify repair.
If the DTC does not return:
Generate readiness code. Refer to => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.
If the DTC does return, no malfunction is detected in the wiring and the voltage supply is OK:
- Replace the Engine Control Module (ECM) (J623). Refer to the Repair Information.
- Assembly is performed in the reverse of the removal.
Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:
1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Modes 01 - 09.
2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.
3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.