GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Tracker - 4WD 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC C1257

Circuit Description

The IG Fuse provides power (12 volts) to the accelerometer. The accelerometer converts the change in vehicle motion, or inertia, into a voltage signal. This signal is sent to the EBCM.

The voltage signal ranges, from 2.4 to 2.6 volts at zero speed change (constant motion) or stationary.The accelerometer voltage signal drops when the vehicle is under acceleration. The accelerometer voltage signal increases when the vehicle is under deceleration.

Conditions for Running the DTC
    • Vehicle is in 4WD
    • Ignition voltage is greater than 9 volts

Conditions for Setting the DTC

A malfunction exists if the vehicle is in 4WD and the EBCM detects:

    • the accelerometer signal circuit voltage is greater than 4.5 volts
    • the accelerometer signal circuit voltage is less than 0.47 volts
    • the accelerometer voltage is between 0.47 and 1.0 volts with all wheel speeds at zero

Action Taken When the DTC Sets
    • ABS is disabled.
    • The ABS warning indicator turns ON.
    • If the malfunction occurs during an ABS event, ABS is disabled after the completion of the ABS event.

Conditions for Clearing the DTC
    • The condition responsible for setting the DTC no longer exists and the Scan Tool Clear DTCs function is used.
    • 100 drive cycles pass with no DTCs detected. A drive cycle consists of starting the vehicle, driving the vehicle over 16 km/h (10 mph), stopping and then turning the ignition OFF.

Diagnostic Aids

Any circuitry that is suspected of causing an intermittent complaint should be thoroughly checked for improper mating, improperly formed or damaged terminals, poor terminal to wiring connections, or physical damage to the wiring harness. If an intermittent condition exists, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

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

  1. Tests for the proper operation of the circuit in the high voltage range.

    2.

  2. Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.

Step

Action

Yes

No

Schematic Reference: Antilock Brake System Schematics

1

Did you perform A Diagnostic System Check - ABS?

Go to Step 2

Go to Diagnostic System Check - ABS

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the Accelerometer Status parameter in the 4WD data list.

Does the scan tool indicate that the Accelerometer Status parameter is OK?

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the Accelerometer.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Accelerometer Status parameter.

Does the scan tool indicate that the Accelerometer Status parameter is Open?

Go to Step 6

Go to Step 4

4

Does the scan tool indicate that the Accelerometer Status parameter is Shorted to Ground?

Go to Step 8

Go to Step 5

5

Does the scan tool indicate that the Accelerometer Status parameter is Unreasonably High or Unreasonably Low?

Go to Step 11

Go to Step 5

6

  1. Turn OFF the ignition.
  2. Connect a 3 amp fused jumper wire between the signal circuit of the Accelerometer harness connector and the ground circuit of the Accelerometer harness connector.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Accelerometer Status parameter.

Does the scan tool indicate that the Accelerometer Status parameter is Shorted to Ground?

Go to Step 11

Go to Step 7

7

Test the 12 volt reference circuit of the Accelerometer 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 15

Go to Step 9

8

Test the signal circuit of the Accelerometer for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 11

9

Test the signal circuit of the Accelerometer for a short to voltage, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 10

10

Test the ground circuit of the Accelerometer for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 12

11

Inspect for poor connections at the harness connector of the accelerometer. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 13

12

Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 15

Go to Step 14

13

Inspect the accelerometer mounting bracket for damage or proper positioning. If the accelerometer is properly mounted and no damage is present, replace the accelerometer. Refer to Lateral Accelerometer Replacement .

Did you complete the replacement?

Go to Step 15

--

14

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

Did you complete the replacement?

Go to Step 15

--

15
  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.

Does the DTC reset?

Go to Step 2

System OK