GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The engine control module (ECM) determines engine misfire by detecting variations in crankshaft speed. Crankshaft speed variations can also occur when a vehicle is operating over a rough road. The wheel speed sensor produces an alternating current (AC) voltage that increases with wheel speed. The ECM receives a rough road signal from an electronic brake control module (EBCM), if equipped with the anti-lock brake system (ABS). The ABS can determine if the vehicle is on a rough road surface based on the signal from each wheel speed sensor. On vehicles with Non-ABS, a rough road signal is sent from a wheel speed sensor located at the left front wheel to the ECM. The ECM can determine if the vehicle is on a rough road surface based on the signal from the wheel speed sensor. When the ECM detects a rough road condition, misfire diagnostics will be disabled. If the ECM detects an incorrect rough road signal, this DTC sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P1385 Wheel Speed Sensor Circuit

Conditions for Running the DTC

    •  DTCs P0501 and P1504 are not set.
    • The vehicle speed is more than 5 km/h (3 mph).
    • DTC P1385 runs continuously once the above conditions are met.

Conditions for Setting the DTC

The ECM does not detect a rough road signal for more than 30 seconds.

Action Taken When the DTC Sets

    • The malfunction indicator lamp (MIL) will not illuminate.
    • The ECM will store conditions which were present when the DTC was set as Failure Records data only.
    • This information will not be stored in the Freeze Frame data.

Conditions for Clearing the MIL/DTC

    • A history DTC will clear after 40 consecutive warm-up cycles without a fault.
    • DTCs can be cleared by using the scan tool.
    • Disconnect the ECM battery feed for more than 10 seconds.

Diagnostic Aids

If the wheel speed sensor harness is damaged in any way, DO NOT repair the harness.

For an intermittent condition, refer to Intermittent Conditions .

Test Description

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

  1. This step determines if an intermittent condition is current.

  1. This step determines if the wheel speed sensor is unable to generate the proper voltage.

Step

Action

Values

Yes

No

Schematic References: Engine Controls Schematics

Connector End View References: Engine Control Module Connector End Views or Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check - Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Start the engine.
  2. Operate the vehicle within the Conditions for Running the DTC.
  3. Observe the DTC Information with a scan tool.

Did DTC P1385 fail this ignition?

--

Go to Step 4

Go to Step 3

3

  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Does the DTC fail this ignition?

--

Go to Step 4

Go to Diagnostic Aids

4

Is the vehicle equipped with an antilock brake system (ABS)?

--

Go to Step 5

Go to Step 7

5

Is the ABS lamp ON?

--

Go to Diagnostic System Check - ABS

Go to Step 6

6

  1. Turn OFF the ignition.
  2. Disconnect the electronic brake control module (EBCM).
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from rough road signal circuit at the EBCM harness connector to a good ground.

Is the voltage within the specified range?

4.8-5.2 V

Go to Step 14

Go to Step 10

7

  1. Disconnect the wheel speed sensor.
  2. Turn ON the ignition, with the engine OFF.
  3. Measure the voltage from the rough road signal circuit of the wheel speed sensor to a good ground with a DMM.

Is the voltage within the specified range?

4.8-5.2 V

Go to Step 8

Go to Step 11

8

  1. Turn OFF the ignition.
  2. Measure the resistance of the low reference circuit of the wheel speed sensor to a good ground with a DMM.

Is the resistance less than the specified value?

5 ohms

Go to Step 9

Go to Step 12

9

Important: If the wheel speed sensor harness is damaged in any way, DO NOT repair the harness.

    Notice: Support the lower control arms in the normal horizontal position in order to avoid damage to the drive axles. Do not operate the vehicle in gear with the wheels hanging down at full travel.

  1. Raise and support the drive wheels.
  2. Start and idle the engine.
  3. Engage the transmission into 2nd gear or drive for an automatic.
  4. Turn the DMM to the AC scale.
  5. Measure the voltage between the rough road signal circuit and low reference of the wheel speed sensor at the sensor side with a DMM.

Is the voltage more than the specified value?

70 mV

Go to Step 15

Go to Step 13

10

Test the rough road signal circuit between the electronic brake control module (EBCM) and the engine control module (ECM) for one of the following conditions:

    • An open
    • A short to ground
    • A short to voltage
    • High resistance

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 15

11

Test the rough road signal circuit of the wheel speed sensor for one of the following conditions:

    • An open
    • A short to ground
    • A short to voltage
    • High resistance

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 15

12

Test the low reference circuit of the wheel speed sensor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 15

13

Test for an intermittent and for a poor connection at the wheel speed sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 16

14

Test for an intermittent and for a poor connection at the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 17

15

Test for an intermittent and for a poor connection at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 18

16

Replace the wheel speed sensor.

Did you complete the replacement?

--

Go to Step 19

--

17

Replace the EBCM. Refer to Brake Pressure Modulator Valve Assembly Replacement in Antilock Brake System.

Did you complete the replacement?

--

Go to Step 19

--

18

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

--

Go to Step 19

--

19

  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 20

20

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK