P1643

CIRCUIT DESCRIPTION
A dash light, wait to start, is illuminated by the powertrain control module (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.

CONDITIONS FOR RUNNING THE DTC
The wait to start lamp is requested ON, test 1.
or
The voltage on wait to start lamp control circuit is low, near 0 volts, test 2.

CONDITIONS FOR SETTING THE DTC
The voltage on wait to start lamp circuit is high, near battery voltage, test 1.
or
The voltage on wait to start lamp control circuit is low, near 0 volts, test 2.

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
^ Clear the MIL and the DTC with a scan tool.

DIAGNOSTIC AIDS
A faulty bulb or the control circuit shorted to ground will cause a DTC P1643 to set.

TEST DESCRIPTION

Steps 1-12:

The number below refers to the step number on the diagnostic table.
2. Tests the ON and the OFF states. Repeat the command as many times as necessary. When the glow plugs are commanded ON by the scan tool, an internal PCM timer protects the glow plugs from damage by cycling the plugs ON for 3 seconds and OFF for 12 seconds. After the 12 seconds has elapsed, the glow plugs can be commanded ON again.