Refer to
DIESEL PCM, GLOW PLUGS, FUSE-RELAY
Circuit Description
A dash light (Wait To Start) is illuminated by the PCM when the glow plugs are commanded ON. When the PCM is commanding the Wait To Start lamp ON, the voltage potential of the circuit will be low (near 0 volts). When the PCM is commanding the Wait To Start lamp OFF, the voltage potential of the circuit will be high (near battery volts). The primary function of the PCM is to supply the ground for the Wait To Start lamp circuit. This is a type B DTC.
Conditions for Setting the DTC
| • | Wait To Start lamp requested ON. |
| • | Voltage on Wait To Start lamp circuit high (near battery volts). |
or
| • | Wait To Start lamp requested OFF. |
| • | Voltage on Wait To Start lamp control circuit low (near 0 volts). |
Action Taken When the DTC Sets
No Wait To Start lamp.
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL off after three consecutive trips without a fault condition. |
| • | A History DTC will clear when forty consecutive warm-up cycles that the diagnostic does not fail (coolant temperature has risen 5°C (40°F) from start up coolant temperature and engine coolant temperature exceeds 71°C (160°F) that same ignition cycle. |
| • | Use of a Scan tool |
Diagnostic Aids
A faulty bulb or the control circuit shorted to ground will cause a P1643 to set.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
-
Repeat the command as many times as necessary (when glow plugs are commanded ON by the scan tool, an internal PCM timer protects the glow plugs from damage by cycling them ON for 3 seconds and OFF for 12 seconds. After the 12 seconds has elapsed, the glow plugs can be commanded ON again).
-
If no trouble is found in the control circuit or the connection at the PCM, the PCM maybe malfunctioning, however, this is an extremely unlikely failure.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 |
Important: Before clearing DTC(s) use the scan tool to record freeze frame and failure records for reference, as data will be lost when Clear Info function is used. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||||
Does the lamp turn ON? | -- | |||||||||
3 | DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids. If additional DTCs were stored refer to those table(s). Are additional DTC(s) stored? | -- | Go to the Applicable DTC table | Go to Diagnostic Aids | ||||||
4 |
Is the lamp OFF? | -- | ||||||||
5 | With a fused jumper wire connected to ground, probe the Wait To Start lamp control circuit in the PCM harness connector. Is the lamp ON? | -- | ||||||||
6 | Check connections at PCM. Was a repair performed? | -- | ||||||||
7 | Wait To Start control circuit is shorted to ground, repair as necessary. Is the action complete? | -- | -- | |||||||
8 | Check the Wait To Start circuit for the following.
Was a repair performed? | -- | -- | |||||||
Replace the PCM. Important: The new PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||||||||
10 |
Does the Scan Tool indicate that the diagnostic Passed? | -- | ||||||||
11 | Using the Scan Tool, select Capture Info, Review Info. Are any DTCs displayed that have not been diagnosed? | -- | Go to the Applicable DTC Table | System OK |
