07 LBZ duramax fault code p0381 ( wait to start lamp control circut)

[Nytroxpress]

The other day I notice my glow plug light would not come on and my CEL took its place. The code was 0381. I decided to allow the motor to cool to ambient temperature and tried again this time watching the volt gauge. It started to rise up stopping about at 11v stayed there for about 5 seconds then built up again. I looked on Mr Google for answers and never come up with a definite one. I did a few test of fuses including the glow plug 125a under the fuse box in the engine bay all tested ok. I removed the lower cover on the steering wheel and tested the pink wire ( test light come on). The next step was to rip apart the guage cluster and check the bulb (if possible) but had to come back to work so next set of days off I guess. Any one experience this code and have any suggestions where to look or test before I just start buying parts to throw at it. I could just leave it be as the glow plugs appear to work but I'm not that way.

 

[prelude48]

Here is a copy and paste from AllData with that code description and operation, follow this and you should find your problem. DTC P0381

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. See: Vehicle > Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0381
- Wait To Start Lamp Control Circuit

Diagnostic Fault Information

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Circuit/System Description

Ignition voltage is supplied directly to the wait to start indicator. The engine control module (ECM) controls the lamp by grounding the control circuit via an internal switch called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the ECM. When the ECM is commanding a component ON, the voltage of the control circuit should be low, near zero volts. When the ECM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be high, near battery voltage. If the fault detection circuit senses a voltage other than what is expected, the fault line status will change causing the DTC to set.

Conditions for Running the DTC

The ignition voltage is greater than 6 volts but less than 18 volts.

Conditions for Setting the DTC

* The ECM detects that the commanded state of the driver and the actual state of the control circuit do not match.
* The condition must be present for a minimum of 5 seconds.

Action Taken When the DTC Sets

* The ECM stores the DTC information in memory.
* The ECM records the operating conditions at the time the DTC sets. The ECM displays the failure information in the Failure Records on the scan tool.

Conditions for Clearing the DTC

* The history DTC clears after 40 malfunction-free warm-up cycles.
* The DTC becomes history when the conditions for setting the DTC are no longer present.
* The ECM receives the clear code command from the scan tool.

Diagnostic Aids

Using the Failure Records data may help locate an intermittent condition. If you cannot duplicate the DTC, the information in the Failure Records can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can help determine how many ignition cycles that the diagnostic test reported a pass and/or a fail.

The wait to start indicator illuminates only with the ignition ON and the engine OFF. The wait to start indicator will not illuminate during post-start glow plug operation. The wait to start indicator will not stay ON for long at higher engine temperatures.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector X2 at the ECM.
2. Ignition ON, verify that the wait to start indicator is OFF.

◊If not OFF, test the wait to start indicator control signal circuit for a short to ground. If the circuit tests normal, replace the instrument panel cluster (IPC).

3. Install a 3-amp fused jumper between the wait to start control signal circuit and ground. Verify that the wait to start indicator is ON.

◊If not ON, test the wait to start indicator control signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the IPC.

4. If all circuits test normal, replace the ECM

 

[Nytroxpress]

Wow. Lots of info their. Thanks I'll attempt it and see where it goes
Thanks

 

[tex78]

Using the 3 amp fuse loads the circuit that may test fine, but fails with load

Bet any money that bad wire from ecm rubbing on lh wheel well liner, very common issue for many things

sent while drinking tea's