Engine Control Module: Testing and Inspection

When checking or correcting engine component malfunctions, check basic engine components prior to troubleshooting the Electronic Control Unit (refer to ON-BOARD DIAGNOSTICS).

1. Using the procedures contained in ON-BOARD DIAGNOSTICS extract all malfunction codes. Diagnosis memory is erased if the battery or the ECU connector is disconnected. Do not disconnect the battery before the trouble codes are completely read. When battery voltage is low, trouble codes cannot be read. If a sensor connector is disconnected with the ignition switch turned on, the diagnosis code is memorized. Be sure to check the battery for voltage and other conditions before starting the test.

On-Board Diagnostics Check Terminal Location:

2. Does the ECU output a steady 12 VDC at the diagnostic check connector? If so the ECU is operating correctly and has no stored trouble codes.
NOTE: Before replacing an ECU that is found to be faulty, insure that no other condition exists that will damage the new unit. This can be best done by testing the inputs and outputs to the ECU for over voltage/inappropriate power readings or grounds. Use the ECU Terminal Identification image and the individual component testing procedures to Identify the correct readings for each pin. Check all pins (at the harness with the ECU removed) that supply a signal to the ECU, for their correct readings and check all other pins to insure that there are no uncalled for voltage readings or grounds present.

To test the Electronic Control Unit (ECU) the ECI checker is recommended, although the tests on the ECI System Check Procedures Chart, can be performed with the use of a suitable multi-meter.

ECU Probing Technique:

NOTE: To test pins using a multi-meter do not remove the connector from the ECU, instead insert a straight pin or needle from the back side of the connector to access each pin.
To use the ECI Checker, proceed as follows.
STEP #1
1. Turn the ignition switch to "LOCK".
2. Remove the ECU cover and the 13 pole harness connector and the 24 pole harness connector from the ECU (computer).
3. Set the check switch of the ECI checker to "off".
4. Set the select switch of the ECI checker to "A".

ECI Box:

5. Connect the WHITE ECI harness connectors to the connectors of the ECI checker, then connect the ECI harness to the ECU and harness connectors. Place the ECI checker on the front passenger seat of the vehicle.

ECI System Check Chart:

ECI System Check:

6. Perform checks according to the ECI System Check Procedures Chart- step 1.

STEP #2

7. Turn ignition switch to lock.
8. Set the check switch of the ECI checker to "off".

ECI BOX:

9. Disconnect the WHITE ECI harness connectors from the connectors of the ECI checker, then connect the GREEN ECI harness connectors of the ECI checker to the connectors of the ECI checker and then connect the ECI harness to the ECU and harness connectors.

System Check Step 2:

10. Perform checks according to the ECI System Check Procedures Chart- step 2. If the checks show any departure from specifications, check the corresponding sensors and related electrical wiring.
11. After repair, recheck with the ECI checker to confirm proper operation.
12. Set the check switch of the ECI checker to "off".
13. Turn the ignition switch to "off".
14. Disconnect the ECI checker and harness from the ECU and body harness connectors. Make sure that the power has been removed from the ECU for at least 15 seconds as this will erase the memory.
15. Connect the body harness connectors to the ECU.
16. After completetion of the test/repairs, be sure to perform a Complete road test to verify that the trouble has been eliminated.