DTC Descriptor
DTC P0381: Wait To Start Lamp Control CircuitDiagnostic Fault Information
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Wait To Start Signal Circuit | P0381 | P0381 | P0381 | -- |
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.
Reference Information
Schematic Reference
| • | Engine Controls Schematics for the 7.8L engine |
Connector End View Reference
| • | Engine Control Module Connector End Views for the 7.8L engine |
Electrical Information Reference
Scan Tool Reference
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the instrument panel cluster (IPC).
- Connect a test lamp between the control circuit and the voltage supply circuit.
- Ignition ON, command the wait to start indicator ON and OFF with the scan tool. The test lamp should turn ON and OFF when changing between the commanded states.
- If all circuits test normal, replace the IPC.
| ⇒ | If the test lamp remains ON all the time, test for a short to ground on the control circuit. If the circuit tests normal, replace the ECM. |
| ⇒ | If the test lamp remains OFF all the time, test for a short to voltage or an open/high resistance on the control circuit. If the circuit test normal, replace the ECM |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for the ECM or IPC replacement, setup, and programming.
