C1257

Accelerometer Circuit Malfunction - Part 1 Of 2:

Accelerometer Circuit Malfunction - Part 2 Of 2:

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 accelerometer provides additional vehicle speed reference to the EBCM. The voltage signal ranges, from 2.4 to 2.6 volts at zero speed change (constant motion.) 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:
^ a short to ground in the accelerometer signal circuit
^ an open in the accelerometer signal circuit
^ 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 failure 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
Use the enhanced diagnostic function of the Scan Tool in order to measure the frequency of the malfunction.

Any circuitry that is suspected of causing the 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.

TEST DESCRIPTION
The number(s) below refer to the step number(s) on the diagnostic table.
3. Tests for the proper operation of the circuit in the high voltage range.
6. 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.