1998 Chevrolet Silverado Repair Question
Chevrolet Silverado Sensor Problem
The camshaft position (CMP) sensor is a sensor designed to detect changes in a magnetic field. The control module supplies the CMP sensor with signal and ground circuits. Ignition voltage is supplied to the CMP sensor by an independent circuit. The CMP sensor produces a magnetic field whenever the ignition is ON. The CMP sensor is mounted near a reluctor wheel that is attached to the distributor shaft. When the distributor shaft rotates, or when the engine is cranking or running, the reluctor wheel changes the magnetic field. The CMP sensor converts each change in the magnetic field into a PULSE. The number of teeth on the reluctor wheel determines how many pulses the CMP sensor detects per camshaft rotation. The control module uses the CMP sensor signal in order to calculate the correct timing for sequential fuel injection.
If the VCM detects the CMP signal is not synchronized with the CKP sensor signal, this DTC will be set.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
The CMP sensor reference pulse is not detected at the correct time interval once every two crankshaft revolutions.
Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles.
The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tool Freeze Frame/Failure Records.
Conditions for Clearing the MIL or 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.
Use a scan tool in order to clear the DTCs.
Electromagnetic interference from the ignition coil or the spark plug wires could cause a poor signal condition in the CMP signal circuit to the VCM. Ensure the routing of the CMP sensor circuitry is correct. Also check for the installation of aftermarket accessories and harnesses creating an electromagnetic interference.
The step number below refers to the step number in the diagnostic table.
Complete diagnosing all other DTCs before performing this diagnostic.
This step checks for an electromagnetic interference caused by improper harness routing.
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