2000 Chevrolet Astro Repair Question
Chevrolet Astro Coolant Problem
The enhanced ignition system uses the Crankshaft Position (CKP) sensor in order to provide a timing input to the control module. Ignition control (IC) spark timing for each cylinder based on this input. The control module provides the ignition timing signal to the Ignition Control Module (ICM) to control the ignition coil. Each timing pulse detected by the ICM allows it to energize the ignition coil. A large secondary ignition voltage is induced in the secondary coil by the primary coil. This high voltage is switched to the correct spark plug by the distributor.
This DTC will set if the VCM detects an unusually high voltage on the ignition timing signal circuit.
CONDITIONS FOR RUNNING THE DTC
The ignition control is enabled.
The engine speed is less than 250 RPM.
CONDITIONS FOR SETTING THE DTC
The ignition control voltage is more than 4.9 volts.
ACTION TAKEN WHEN THE DTC SETS
The control module illuminates the Malfunction Indicator Lamp (MIL) the first time the diagnostic runs and fails.
The control module will set the DTC and records the operating conditions at the time the diagnostic fails. The control module stores the failure information in the scan tools Freeze Frame/Failure Records.
CONDITIONS FOR CLEARING THE MIL/DTC
The control module turns OFF the MIL after 3 consecutive drive trips when the test has Run and Passed.
A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle.
A scan tool can clear the DTCs.
Inspect for intermittents. If the connections and the harness are OK, monitor a Digital Multimeter (DMM) connected between VCM terminal C3 pin 9 and C4 pin 18 while moving the related connectors and the wiring harness. If the failure is induced, the voltage reading will change. This may help to isolate the location of the malfunction.
An intermittent may be caused by any of the following conditions:
A poor connection
Rubbed through wire insulation
A broken wire inside the insulation
Thoroughly inspect any circuitry that is suspected of causing the Intermittent complaint. Refer to Testing for Intermittent and Poor Connections in Diagrams.
If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Diagrams.
The numbers below refer to the step numbers in the diagnostic table.
This test determines if the DTC is an intermittent.
This step checks if the IC signal from the VCM is available at the ICM.
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