DDEC III/IV Single ECM Troubleshooting – Section 10.1 Intermittent Code or a Symptom and No Codes

Section 10.1
Intermittent Code or a Symptom and No Codes

The following procedure will diagnose an intermittent code or symptom.‪

Section 10.1.1
Diagnosis by Symptom

Perform the following steps to diagnose an intermittent code or symptom.‪

Note: Do not use any other procedures (except for the suggestions listed in this guide) when trying to solve an intermittent problem. Use of any other procedures for this type of problem can result in the replacement of non-defective parts.

Many intermittent problems are caused by faulty electrical connectors or wiring. Diagnosis must include a careful inspection of the indicated circuit wiring and connectors. For example, an intermittent code 35 (Oil Pressure Sensor High Voltage) would indicate a problem in the following areas associated with the Oil Pressure Sensor.‪

• Wires #530 (signal line), #416 (+5 volt line), or #452 (ground line)
• The Oil Pressure Sensor connector or ECM connector
• An intermittent problem in the Oil Pressure Sensor (least likely)

Use the following checklist:‪

1. Check for poor mating of the connector halves or terminals not fully seated in the connector body (backed out terminals).
2. Look for improperly formed or damaged terminals. All connector terminals in the problem circuit should be carefully inspected to determine proper contact tension. Use a mating terminal to test the contact tension.
3. Electrical system interference caused by a defective relay, ECM driven solenoid, or a switch causing an electrical surge. Look for problems with the charging system (alternator, etc.). In certain cases, the problem can be made to occur when the faulty component is operated as in the case of a relay.
4. Verify alternator grounds are clean and making good contact. Disconnect the alternator belt to test.
5. Wiggle wires and harnesses to try to make the problem active, or occur again.

Section 10.1.2
Verify Repairs

Perform the following steps to verify repairs.‪

1. Clear codes.
2. Confirm the CEL does not come on (except for the five second ignition ON bulb check).
3. Run the engine for one minute.
4. If the CEL stays ON, refer to "9.1.2 Read Active Codes" .