Circuit Description
Ignition voltage is supplied directly to the wait to start indicator. The powertrain control module (PCM) 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 PCM. When the PCM is commanding a component ON, the voltage of the control circuit should be low, near 0 volts. When the PCM 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.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0381 Wait To Start Lamp Control Circuit
Conditions for Running the DTC
The ignition voltage is greater than 6 volts but less than 18 volts.
Conditions for Setting the DTC
| • | The PCM 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 PCM stores the DTC information in memory. |
| • | The PCM records the operating conditions at the time the DTC sets. The PCM 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 PCM receives the clear code command from the scan tool. |
Diagnostic Aids
Important: Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.
Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can aid in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also aid determining how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed.
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.
For an intermittent, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Instrument Cluster Schematics Connector End View Reference: Engine Control Module Connector End Views in Engine Controls - 6.6L (LLY) | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 | Turn the ignition ON, with the engine OFF. Does the wait to start indicator illuminate and then turn OFF? | -- | Go to Diagnostic Aids | Go to Step 3 |
3 |
Does the voltage measure greater than the specified value? | 9.5 V | Go to Step 4 | Go to Step 6 |
4 | Test the wait to start signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 5 |
5 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 7 |
6 | Repair the short to ground in the wait to start signal circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 8 | -- |
7 | Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 8 | -- |
8 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
