GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2002 🢒 Aztek - FWD 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC C0235-C0237, C035-C037, or P1504

Circuit Description

The RPM signal circuit provides the EBCM with an indication of engine RPM to help determine TCS control methods and rates when a TCS event takes place.

Conditions for Running the DTC
    • The ignition switch is ON and the engine running.
    • After 2 seconds starting, and if there is a undervoltage condition.

Conditions for Setting the DTC

The EBCM does not received an RPM input signal after 1 second, after the engine has been started.

Action Taken When the DTC Sets

If equipped, the following actions occur:

    • A malfunction DTC is stored.
    • The TRAC OFF indicator is turned on.
    • The TCS is disabled. ABS remains functional.

Conditions for Clearing the DTC
    • The condition for DTC is no longer present and the scan tool Clear DTCs function is used.
    • 100 ignition cycles have passed with no DTC(s) detected.

Diagnostic Aids

Perform a thorough inspection of the wiring. Perform a thorough inspection of the connectors. Failure to carefully and fully inspect the wiring and the connectors may result in misdiagnosis. Misdiagnosis causes part replacement with reappearance of the malfunction.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. If the instrument panel tachometer is working properly, the cause of the malfunction is most likely between the PCM and the EBCM, or the EBCM itself.

    2.

  2. At this point, the PCM is likely causing the malfunction. Refer to the OBD system check.

Step

Action

Value(s)

Yes

No

Schematic Reference: Antilock Brake System Schematics Connector End View Reference: Antilock Brake System Connector End Views

or

Powertrain Control Module Connector End Views

1

Did you perform the Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check - ABS

2

  1. Start the engine.
  2. Vary the engine RPM with the throttle while observing the IP tachometer.

Does the IP tachometer work properly as the engine RPM changes?

--

Go to Step 3

Go to Step 9

3
  1. Turn the ignition switch to the OFF position.
  2. Disconnect the PCM connector C2 from the PCM.
  3. Disconnect the EBCM connector from the EBCM.
  4. Install the J 39700 universal pinout box with the J 39700-530 cable adapter to the EBCM harness only.
  5. Use a J 39200 digital multimeter to measure the resistance between the PCM harness connector tach signal circuit, and the universal breakout box terminal 11.

Is the resistance within the specified range?

0-5 ohms

Go to Step 4

Go to Step 10

4

Use a J 39200 digital multimeter to measure the resistance between the universal breakout box terminal 11 and a good ground.

Is the resistance within the specified range?

0L

Go to Step 5

Go to Step 11

5
  1. Turn the ignition switch to the ON position
  2. Use a DMM to measure the voltage between the universal breakout box terminal 11 and a good ground.

Is the voltage within the specified range?

0-2 V

Go to Step 6

Go to Step 12

6
  1. Inspect the PCM connector C2 for the following:
    2. • Inspect for damage.
    • Inspect for poor terminal contact.
    • Inspect for corrosion.
  2. Inspect the EBCM connector for the following:
    3. • Inspect for damage.
    • Inspect for poor terminal contact.
    • Inspect for corrosion.
  3. Ensure both the PCM connector C2 and the EBCM connector are properly retained when connected.

Are the following signs present on either connector:

    • Is poor terminal contact present?
    • Is corrosion present?
    • Is damaged terminals present?

--

Go to Step 13

Go to Step 7

7
  1. Reconnect all the connectors.
  2. Using the scan tool clear the DTC.
  3. Disconnect the scan tool from the DLC.
  4. Start the engine.

Did DTC C0236 reset?

--

Go to Step 8

Go to Diagnostic System Check - ABS

8

Replace the EBCM. Refer to Electronic Brake Control Module Replacement .

Is the repair complete?

--

Go to Step 14

--

9

Check the PCM. Refer to Diagnostic System Check - Engine Controls in Engine Controls.

Is the repair complete?

--

Go to Step 14

--

10

Repair an open between PCM and EBCM tach signal circuit. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 14

--

11

Repair a short to ground in tach signal circuit. Refer to Wiring Repairs Wiring Systems.

Is the repair complete?

--

Go to Step 14

--

12

Repair a short to voltage in TACH signal circuit. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 14

--

13

Replace all the terminals or replace the connectors that exhibit signs of the following:

    • That exhibit signs of poor terminal contact.
    • That exhibit signs of corrosion.
    • That exhibit signs of damaged terminals.

Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 14

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14
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Dose the DTC reset?

--

Go to Step 2

System OK