Engine Control Module: Testing and Inspection
Motronic Engine Control Module
Motronic Engine Control Module (ECM) (J220) regulates fuel injection, Throttle Valve Control Module (J338), oxygen sensor regulation, ignition, knock control, Evaporative Emission (EVAP) Canister Purge Regulator Valve (N80), engine speed limitation through fuel injectors or Fuel Pump (FP) Relay (J17) as well as On Board Diagnostic (OBD).
Motronic Engine Control Module Voltage Supply, Checking
Special tools, testers and auxiliary items required
• Multimeter.
• Wiring diagram.
Test requirements
• The Motronic Engine Control Module (ECM) (J220) 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 (GND) connections between engine/transmission/chassis OK.
• Ignition switched off.
Test procedure
- Perform a preliminary check to verify the customers complaint. Refer to => [ General Diagnosis ] General Diagnosis.
Start diagnosis
- Remove the Motronic Engine Control Module (ECM) Power Supply Relay (J271).
Checking voltage
- Using a Multimeter, check the Motronic Engine Control Module (ECM) Power Supply Relay (J271) socket 1/30 to Ground (GND).
Specified value: battery voltage.
If the specified value was not obtained:
- Check the wiring connections from the Battery to the Motronic Engine Control Module (ECM) Power Supply Relay (J271) socket 1/30 for an open circuit or a short circuit.
- Check the wiring connections for damage, corrosion, lose 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 Motronic Engine Control Module (ECM) Power Supply Relay (J271) socket 3/86 to Ground (GND).
Specified value: battery voltage.
If the specified value was obtained:
Checking wiring
If the manufacturers test box is being used. Perform the following step.
- Install the test box. Refer to repair information.
If the manufacturers test box is not being used. Perform the following step.
- Remove the Motronic Engine Control Module (ECM) (J220).
- Using a Multimeter, check the Motronic Engine Control Module (ECM) Power Supply Relay (J271) socket 3/86 to the Motronic Engine Control Module (ECM) (J220) electrical harness connector T121 terminal 62 for resistance.
Specified value: 2.0 ohms Max.
If the specification was not obtained:
- Check the wiring for a short circuit to each other, Battery (+), and Ground (GND).
- Check the electrical harness connector for damage, corrosion, lose or broken terminals.
- If necessary, repair the faulty wiring connection.
If no malfunction is found in the wiring:
Checking activation
- Switch the ignition on.
- Using a Multimeter, check the Motronic Engine Control Module (ECM) Power Supply Relay (J271) socket 4/85 to the Motronic Engine Control Module (ECM) (J220) electrical harness connector T121 terminal 23 for voltage.
- Switch the ignition off.
Specified value: 0.5 V Max.
If the specified value was obtained:
- Replace the Motronic Engine Control Module (ECM) Power Supply Relay (J271).
If the specified value was not obtained:
- Check the wiring connection for an open circuit, short circuit to Battery (+) or Ground (GND).
- Check the wiring connection for damage, corrosion, lose or broken terminals.
- If necessary, repair the faulty wiring connection.
If no malfunction is found in the wiring and voltage supply was not OK:
- Replace the Motronic Engine Control Module (ECM) (J220).
Final procedures
After repair work, the following work steps must be performed in the following sequence:
1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Mode 03 - Read DTC Memory.
2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Mode 04 - Erase DTC Memory.
3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Readiness Code.
- End of diagnosis.