P1643

DTC P1643 Wait to Start Lamp Control Circuit






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 tamp 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

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°(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

5. 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).

9. If no trouble is found in the control circuit or the connection at the PCM, the PCM maybe malfunctioning, however, this 15 an extremely unlikely failure.