10.1 INTERMITTENT CODE OR A SYMPTOM AND NO CODES
The following procedure will diagnose an intermittent code or symptom.
Diagnosis by Symptom
Perform the following steps to diagnose an intermittent code or symptom.
Do not use any other procedures (except for the suggestions listed in this manual) 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 re-occur.
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 section 9.1.2.
All information subject to change without notice.
6SE497 9709 Copyright © 1997 DETROIT DIESEL CORPORATION