Circuit Description
The Camshaft Position (CMP) sensor works in conjunction with a single tooth reluctor wheel on the Bank 2 Intake camshaft. The ECM pulls up the CMP sensor signal circuit to 12 volts and monitors this voltage. As the reluctor wheel tooth rotates past the sensor, the sensor's internal circuitry pulls the signal circuit to ground, creating a square wave signal that is used by the ECM. The reluctor wheel tooth covers 180 degrees of the camshaft circumference. This causes the CMP signal voltage to transition once per crankshaft revolution. This signal, when combined with the CKP sensor signal, enables the ECM to determine exactly which cylinder is on a firing stroke. The ECM can then properly synchronize the ignition system, the fuel injectors and the knock control. Note that as long as the CKP signal is available, the engine can start even if there is no CMP sensor signal. The ECM will default to a non-sequential fuel injector operation.
Conditions for Running the DTC
The engine speed is greater than 22 RPM.
Conditions for Setting the DTC
| • | The CMP signal is incorrect for at least 500 milliseconds. |
| • | The engine has completed at least 100 revolutions. |
Action Taken When the DTC Sets
| • | The ECM illuminates the Malfunction Indicator Lamp (MIL) and records the operating conditions in the Freeze Frame on the second consecutive drive trip that the diagnostic runs and fails. |
| • | The ECM will use a calculated spark retard value in order to minimize a knock during conditions when a knock is likely to occur. The calculated value will vary based on the engine speed and load. |
| • | The ECM will energize all of the ignition poles at full intensity in order to compensate for a lost sense of position. |
Conditions for Clearing the MIL/DTC
| • | The ECM turns OFF the MIL after three consecutive drive trips that the diagnostic runs and passes. |
| • | A History DTC clears after forty consecutive warm-up cycles in which no failures are reported by this diagnostic or any other emission related diagnostic. |
| • | The ECM battery voltage is interrupted. |
| • | The scan tool clears the MIL/DTC. |
Diagnostic Aids
Use the Connector Test Adapter Kit J 35616 for any test that requires probing the ECM harness connector or a component harness connector. Using this kit will prevent damage to the harness connector terminals.
Check for the following conditions:
| • | Poor connections at the ECM or at the component. Inspect the harness connectors for any backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. Refer to Engine Control Module Diagnosis , Checking Terminal Contact for the proper procedure. |
| • | Misrouted harness. Inspect the harness in order to ensure that the harness is not routed too close to any high voltage wires such as spark plug leads, or too close to any high current devices such as the alternator, the motors, the solenoids, etc. |
| • | Damaged harness. Inspect the wiring harness for any damage. If the harness appears to be OK, observe the scan tool while moving the related connectors and the wiring harnesses. A change in the display may help in order to locate the fault. |
| If the sensor signal is only affected when the harness is moved at a component, and there is no problem with the harness or the connections, the component may be damaged. |
| • | Check the sensor for a proper installation. A sensor that is loose or not fully seated (causing an excessive air gap between the sensor and the reluctor wheel) may cause this DTC to set. |
Refer to Symptoms for the Intermittents.
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System check? | -- | ||||||
2 |
Does the cam signal toggle between low and high? | -- | Problem is intermittent. Refer to Diagnostic Aids | |||||
3 |
Does the DVM indicate the specified voltage? | B+ | ||||||
4 | Measure the voltage from the CMP signal circuit in the harness connector (ECM side) to battery ground with the DVM J 39200 . Does the DVM indicate the specified voltage? | B+ | ||||||
5 |
Is continuity indicated? | -- | ||||||
6 | Check the harness for continuity between the CMP sensor signal circuit and battery ground with the DVM J 39200 . Is continuity indicated? | -- | ||||||
7 | Probe the CMP sensor shielded ground circuit in the harness connector (ECM side) with the test light J 34142-B connected to B+. Does the test light illuminate? | -- | ||||||
Was a problem found and corrected? | -- | |||||||
9 |
Does the scan tool toggle between low and high? | -- | ||||||
10 | Repair the Switched B+ circuit. Is the action complete? | -- | -- | |||||
11 | Repair the short to ground in the signal circuit. Is the action complete? | -- | -- | |||||
12 | Repair the open/high resistance in the signal circuit. Is the action complete? | -- | -- | |||||
13 | Check the CMP sensor for the following conditions:
Was a problem found and corrected? | -- | ||||||
14 | Replace the CMP sensor. Is the action complete? | -- | -- | |||||
15 | Check for a poor connection or poor terminal tension at the ECM harness connector. Refer to Electrical Diagnosis in Engine Electrical, and Troubleshooting Procedures for the proper procedure. Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis . Was a problem found and corrected? | -- | ||||||
16 |
Important: This vehicle is equipped with a Theft Deterrent System which interfaces with the Engine Control Module (ECM). Program the new ECM with the frequency code of the theft deterrent module that is currently on the vehicle. Replace the ECM. Refer to Engine Control Module Replacement/Programming . Is the action complete? | -- | -- | |||||
17 |
Is this DTC set? | -- | ||||||
18 | Were there any additional DTCs noted during the Powertrain OBD System Check that have not been diagnosed? | -- | Go to the applicable DTC table | The System is OK |
