Circuit Description
The Camshaft Position (CMP) Sensor detects the rotational speed of the camshaft. As the camshaft rotates, an AC signal is generated in the CMP Sensor. This signal provides the input to the Transmission Control Module (TCM), to determine engine speed. The engine speed is used for various calculations including Torque Converter Clutch (TCC) slip speed and overdrive ratio.
If the TCM detects low output signal voltage, then DTC 71 sets.
Conditions for Setting the DTC
| • | No DTC 28. |
| • | Engine speed less than 50 RPM. |
| • | Transmission range indicates R, D4, D3 or D1. |
| • | All conditions are met for 2 seconds. |
Action Taken When the DTC Sets
| • | The TCM inhibits TCC. |
| • | DTC 71 is stored in TCM history. |
Conditions for Clearing the DTC
| • | The TCM clears the DTC from Current to History when the fault condition(s) no longer exist and the ignition switch is cycled OFF and then ON. |
| • | A scan tool can clear the DTC from Current and History status. The TCM clears the DTC from the TCM history if the vehicle completes 40 ignition cycles without a failure reported. |
| • | The TCM cancels the DTC default actions when the fault no longer exists and the ignition is cycled OFF and then ON. |
Diagnostic Aids
| • | Inspect the wiring at the TCM, the transmission connector and all other circuit connecting points for the following conditions: |
| - | A bent terminal |
| - | A backed out terminal |
| - | A damaged terminal |
| - | Poor terminal tension |
| - | A chafed wire |
| - | A broken wire inside the insulation |
| - | Moisture intrusion |
| - | Corrosion |
| • | A mechanical problem with the camshaft may set this code. With CMP Sensor removed, check camshaft and CMP Sensor drive gear for damage. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step verifies the fault.
-
This step indicates that the sensor is capable of inducing an AC voltage in the circuit.
-
This step checks circuits 935 and 452 for being shorted together.
-
This step checks the entire CMP Sensor circuit for proper signal output.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Were you sent here from the "Powertrain On-Board Diagnostic (OBD) System Check?" | -- | ||
Important:: Before clearing the DTC's, record the Current and History DTC's information for reference. The Clear Info function erases the stored Current and History DTC from the TCM. Does the Engine Speed on the Scan Tool increase, as the engine speed increases? | -- | System OK Refer to Diagnostic Aids | ||
Is the AC voltage greater than the specified value? | 0.5 volts AC | |||
4 |
Is the voltage within the specified value? | 4.0 - 5.2 volts DC | ||
5 | Is the voltage reading from Step 4 greater than the specified value? | 4.0 - 5.2 volts DC | ||
6 | Inspect circuit 935 for a short to B +. Refer to General Electrical Diagnosis . Did you find a condition? | -- | ||
7 | Connect the J 39200 DMM between terminals A and B of the CMP Sensor connector. Is the voltage within the specified value? | 4.0 - 5.2 volts DC | ||
8 | Inspect circuit 935 for high resistance or an open. Refer to General Electrical Diagnosis . Did you find a condition? | -- | ||
9 | Are there any other sensor DTC's? | -- | ||
10 | Inspect for an open in the sensors' ground circuit 452. Refer to General Electrical Diagnosis . Did you find a condition? | -- | ||
11 | Inspect for an open in circuit 452 from the CMP Sensor connector terminal B, to the sensors' ground splice. Did you find and repair the problem? | -- | -- | |
Is the resistance less than the specified value? | 50 kohms | |||
Is the voltage greater than the specified value? | 0.5 volts AC | Go to Diagnostic Aids | ||
14 | Repair circuits 935 and 452 for being shorted together. Did you repair the condition? | -- | -- | |
15 | Remove the CMP Sensor Assembly and inspect the driven gear and the camshaft for damage. Did you find a condition? | -- | ||
16 | Refer to Unit Repair Section for the proper repair of CMP Sensor Assembly, driven gear or camshaft. Is the repair complete? | -- | -- | |
17 | Replace the CMP Sensor. Is the replacement complete? | -- | -- | |
18 | Replace the TCM. Refer to DTC 51 PROM Error TCM Replacement. Is the replacement complete? | -- | -- | |
19 |
Start the engine and run at idle speed. Is the engine speed greater than 50 RPM for two seconds? | -- | System OK | Begin Diagnosis again |
