Diagnostic Instructions
DTC Descriptor
DTC P1390: Wheel Speed Sensor Circuit wo/ABS
DTC P1396: Wheel Speed Sensor Circuit w/ABS
Circuit/System 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.
Conditions for Running the DTC
• | The engine is running. |
• | The DTC runs continuously once the above condition is met. |
Conditions for Setting the DTC
P1390
The ECM detects the voltage on the rough road signal circuit of the wheel speed sensor is less than 1 volt, greater than 5 volts, or difference between the minimum and maximum voltage is greater than 5 volts.
P1396
The ECM detects an invalid rough road signal from the EBCM.
Action Taken When the DTC Sets
DTC P1390 and P1396 are Type C DTCs.
Conditions for Clearing the DTC
DTC P1390 and P1396 are Type C DTCs.
Reference Information
Schematic Reference
Engine Controls Schematics
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Engine running, observe the DTC information with a scan tool. DTCs P1390 or P1396 should not set.
- Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
Important: If the ABS lamp is illuminated, the ABS system must be diagnosed prior to using this diagnostic procedure. Refer to
Diagnostic System Check - Vehicle.
- Ignition OFF, disconnect the harness connector at the wheel speed sensor or the EBCM - if equipped with ABS.
- Ignition OFF, test for less than 5 ohms of resistance between the rough road low reference circuit terminal 2 and ground.
⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM. |
- Ignition ON, test for 4.8-5.2 volts on the rough road signal circuit terminal 1.
⇒ | If less than the specified range, test the signal circuit for a short to ground or an open. If the circuit tests normal, replace the ECM. |
⇒ | If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM. |
- If all circuits test normal, test or replace the wheel speed sensor or EBCM - if equipped with ABS.
Component Testing
Important: This procedure is for vehicles without ABS. If the wheel speed sensor harness is damaged in any way, DO NOT repair the harness.
- Ignition OFF, disconnect the harness connector at the wheel speed sensor.
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.
- Raise and support the drive wheels.
- Engine running, place the transmission into 2nd gear or drive for an automatic.
- Test for 70 mV AC between the rough road signal terminal 1 and low reference terminal 2.
⇒ | If less than the specified range, replace the wheel speed sensor. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.