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For 1990-2009 cars only

DTC 71 Camshaft Position Sensor Circuit Low L57 MFI


Object Number: 372641  Size: SF
Automatic Transmission Components Diesel
Automatic Transmission Controls Schematics TCM Control
Handling ESD Sensitive Parts Notice

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 Running the DTC

    • No DTC 28.
    • Engine speed less than 50 RPM.
    • Transmission range indicates R, D4, D3 or D1.

Conditions for Setting the DTC

All conditions are met for 2 seconds.

Action Taken When the DTC Sets

    • The TCM inhibits TCC.
    • The TCM stores DTC 71 in TCM history.

Conditions for Clearing the DTC

    • A scan tool clears the DTC from TCM history.
    • The TCM clears the DTC from TCM history if the vehicle completes 40 consecutive key cycles without a diagnostic fault occurring.
    • The TCM cancels the DTC default actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the TCM.

Diagnostic Aids

    • Inspect the wiring at the TCM, the transmission connector and all other circuit connecting points for the following conditions:
       - A backed out terminal
       - A damaged terminal
       - Reduced terminal tension
       - A chafed wire
       - A broken wire inside the insulation
       - Moisture intrusion
       - Corrosion
    • A mechanical condition with the camshaft may set this code. With the CMP sensor removed, the camshaft and CMP sensor drive gear can be checked for damage.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step verifies the fault.

  2. This step indicates that the sensor is capable of inducing an AC voltage in the circuit.

  3. This step checks circuits 935 and 452 for being shorted together.

  4. This step checks the entire CMP sensor circuit for proper signal output.

DTC 71

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

  1. Install the Scan Tool .
  2. Turn the ignition switch to the RUN position.
  3. Important:: Before clearing the DTCs, use the scan tool in order to record the Failure Records. Using the Clear Info function erases the Failure Records from the TCM.

  4. Record the Failure Records.
  5. Clear the DTC.
  6. Place the transmission in PARK.
  7. Start the engine, and select Engine Speed on the Scan Tool .
  8. Slowly accelerate the engine.

Does Engine Speed on the Scan Tool increase as the engine speed increases?

--

System OK

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn the ignition switch OFF.
  2. Disconnect the CMP sensor connector from the sensor.
  3. Connect J 39200 digital multimeter (DMM) to the CMP sensor terminals.
  4. Select AC volts.
  5. Start the engine, and observe the J 39200 DMM.

Is the AC voltage greater than the specified value?

0.5 volts AC

Go to Step 4

Go to Step 15

4

  1. With the engine OFF, turn the ignition switch to the RUN position.
  2. Select DC volts on the J 39200 DMM.
  3. Connect the J 39200 DMM to a good ground.
  4. Measure the voltage in circuit 935 (WHT) at the CMP sensor connector, terminal A.

Is the voltage within the specified value?

4.0-5.2 volts DC

Go to Step 7

Go to Step 5

5

Is the voltage reading from Step 4 greater than the specified value?

4.0-5.2 volts DC

Go to Step 6

Go to Step 8

6

Inspect circuit 935 (WHT) for a short to B+.

Refer to General Electrical Diagnosis in Wiring Systems.

Was a condition found?

--

Go to Step 12

Go to Step 13

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

Go to Step 13

Go to Step 9

8

Inspect circuit 935 (WHT) for high resistance or an open.

Refer to General Electrical Diagnosis in Wiring Systems.

Was a condition found?

--

Go to Step 12

Go to Step 19

9

Are there any other sensor DTCs?

--

Go to Step 10

Go to Step 11

10

Inspect for an open in the sensors' ground circuit 452 (BLK).

Refer to General Electrical Diagnosis in Wiring Systems.

Was a condition found?

--

Go to Step 12

Go to Step 19

11

Inspect for an open in circuit 452 (BLK), from the CMP sensor connector terminal B, to the sensors' ground splice.

Was a condition found?

--

Go to Step 12

--

12

Repair the wiring as necessary.

Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 20

--

13

  1. Turn the ignition switch to the OFF position.
  2. Do not reconnect the CMP sensor connector to the sensor.
  3. Disconnect the TCM connector C1.
  4. Connect the J 39200 DMM to terminals D6 and D7 of the C1 connector.
  5. Select ohms on the J 39200 DMM.

Is the resistance less than the specified value?

50 kohms

Go to Step 15

Go to Step 14

14

  1. Reconnect the CMP sensor connector to the sensor.
  2. With the J 39200 DMM on terminals D6 and D7, select AC volts.
  3. Observe the J 39200 DMM while cranking the engine.

Is the voltage greater than the specified value?

0.5 volts AC

Go to Step 19

Go to Step 16

15

Repair circuits 935 (WHT) and 452 (BLK) for being shorted together.

Is the repair complete?

--

Go to Step 20

--

16

  1. Remove the CMP sensor assembly.
  2. Inspect the driven gear and the camshaft for damage.

Was a condition found?

--

Go to Step 17

Go to Step 18

17

Refer to Camshaft Replacement in Engine Mechanical, for repair of the driven gear or camshaft.

Is the repair complete?

--

Go to Step 20

--

18

Replace the CMP sensor.

Is the replacement complete?

--

Go to Step 20

--

19

Replace the TCM.

Refer to Powertrain Control Module Replacement/Programming in Engine Controls.

Is the replacement complete?

--

Go to Step 20

--

20

Perform the following procedure in order to verify the repair:

  1. Select DTC.
  2. Select Clear Info.
  3. Start the engine and run at idle speed.

Is the engine speed greater than 50 RPM for 2 seconds?

--

System OK

Go to Step 1