GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2005 🢒 Isuzu MD F-Series 🢒 DTC 🢒 DTC P0381

Circuit Description

The wait to start indicator illuminates in the message center when the engine control module (ECM) commands the glow plugs ON. The ECM provides the ground for the wait to start indicator control circuit. The ECM monitors the voltage on the control circuit in order to determine if there is a circuit malfunction. The ECM should detect a low voltage when the indicator is illuminated and a high voltage when the indicator is not illuminated.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0381 Wait to Start Lamp Control Circuit

Conditions for Running the DTC
    • The ignition is in ON.
    • The ignition voltage is between 9-16 volts.

Conditions for Setting the DTC
    • The ECM detects a lower than normal voltage at the control circuit of the wait to start indicator when the ECM commands the indicator to illuminate.
    • The ECM detects a higher than normal voltage at the control circuit of the wait to start indicator when the ECM is not commanding the indicator to illuminate.

Diagnostic Aids

The DTC may be intermittent. For intermittent diagnosis, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. The wait to start indicator illuminates briefly when the ignition is turned ON. The ON time depends upon the temperature of the engine at the time.

    2.

  2. If the fuse opens during this test, there is a short to voltage on the control circuit.

Step

Action

Yes

No

Schematic Reference: Instrument Cluster Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Ensure that the engine is not at full operating temperature.
  2. Turn ON the ignition.
  3. Observe the wait to start indicator in the message center.

Does the wait to start indicator illuminate and then turn OFF?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

Does the wait to start indicator illuminate continuously in the message center?

Go to Step 6

Go to Step 4

4

Does the wait to start indicator not illuminate in the message center with the ignition ON?

Go to Step 5

Go to Diagnostic Aids

5

  1. Turn OFF the ignition.
  2. Disconnect the engine control module (ECM) connector C1.
  3. Connect a 3-ampere fused jumper wire between the wait to start indicator control circuit and a good ground.
  4. Turn ON the ignition, with the engine OFF.

Does the wait to start indicator illuminate in the message center?

Go to Step 10

Go to Step 7

6
  1. Turn the ignition OFF.
  2. Disconnect the ECM connector C1.
  3. Observe the wait to start indicator in the message center.

Does the wait to start indicator illuminate in the message center?

Go to Step 8

Go to Step 10

7

Test the wait to start indicator control circuit for an open, for a short to voltage or for a high resistance. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 9

8

Test the wait to start indicator control circuit for a short to ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 9

9

Inspect for poor connections at the harness connector of the message center. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 11

10

Inspect for poor connections at the harness connector of the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 12

11

Replace the message center. Refer to Telltale Circuit Board Replacement .

Did you complete the replacement?

Go to Step 13

--

12

Replace the ECM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 13

--

13
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTCs as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK