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
| • | The ignition is ON. |
| • | The DTC runs continuously when the above condition is met. |
Conditions for Setting the DTC
The ECM detects the voltage on the rough road signal circuit of the wheel speed sensor is less than 1.5 volts, greater than 2.2 volts, or the difference between the minimum and maximum voltage is greater than 0.06 volt.
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
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 | |||||||||
2 |
Did DTC P1385 fail this ignition? | -- | Go to Step 4 | Go to Step 3 | ||||||||
Does the DTC fail this ignition? | -- | Go to Step 4 | Go to Diagnostic Aids | |||||||||
4 | Is the vehicle equipped with an Anti-Lock Brake System (ABS)? | -- | Go to Step 5 | Go to Step 7 | ||||||||
5 | Is the ABS lamp ON? | -- | Go to Step 6 | |||||||||
6 |
Is the voltage within the specified range? | 4.8-5.2 V | Go to Step 14 | Go to Step 10 | ||||||||
7 |
Is the voltage within the specified range? | 4.8-5.2 Volts | Go to Step 8 | Go to Step 11 | ||||||||
8 |
Is the resistance less than the specified value? | 5 ohms | Go to Step 9 | Go to Step 12 | ||||||||
|
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. 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:
Refer to Circuit Testing and Wiring Repairs . 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:
Refer to Circuit Testing and Wiring Repairs . 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 . 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 . 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 . 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 . 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 . 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 |
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? | -- | System OK | |||||||||
