GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Optra 🢒 Engine 🢒 Engine Controls - 1.8L (L79) 🢒 DTC P1396

Circuit Description

The engine control module (ECM) determines linear wheel speed excessive variation. The wheel speed variation test detects at least 1 missing edge from the wheel speed sensor signal.

Conditions for Setting the DTC
    • WSS variation is greater than 18 km/h (11.2 mph).
    • Vehicle speed is greater than 10 km/h (6.2 mph).

Action Taken When the DTC Sets
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The ECM will store conditions which were present when the diagnostic trouble code (DTC) set as failure records data only. This information will not be stored as freeze frame data.
    • A history DTC is stored.

Conditions for Clearing the MIL/DTC
    • A history DTC will clear after 40 consecutive warm-up cycles without a fault.
    • The DTCs can be cleared by using the scan tool.

Diagnostic Aids

Inspect for the following conditions:

    • Poor connection at the ECM -- Inspect the harness connections for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection.
    • Damaged harness -- Inspect the wiring harness for damage. If the harness appears to be OK, observe the G sensor display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the display will indicate the location of the fault.

An open signal circuit of open pulse width modulation (PWM) serial data line between the ECM and the EBCM will be the cause of this DTC.

Test Description

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

  1. The diagnostic system check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.

    2.

  2. The replacement ECM must be reprogrammed. Refer to the latest Techline procedure for ECM reprogramming.

Step

Action

Yes

No

1

Perform the diagnostic system check.

Was the check performed?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2
  1. Turn ON the ignition, with the engine OFF.
  2. Install a scan tool.

Are any additional DTCs set?

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3
  1. Review and record the scan tool failure records data.
  2. Operate the vehicle within failure records conditions at noted.
  3. Using the scan tool, monitor specific DTC info for DTC P1391.

Does the scan tool indicate that DTC P1391 failed?

Go to Step 4

Go to Diagnostic Aids

4
  1. Turn OFF the ignition.
  2. Disconnect the engine control module (ECM) and inspect for an open or short in the wire between ECM connector terminal K7 and electronic brake control module (EBCM) connector terminal 25.

Is the problem found?

Go to Step 5

Go to Step 6

5

Repair an open or short in the wire between ECM connector terminal K7 and EBCM connector terminal 25.

Did you complete the repair?

Go to Step 7

--

6
  1. Turn OFF the ignition.
  2. Replace the ECM. Refer to Engine Control Module Replacement .

Is the repair complete?

Go to Step 7

--

7
  1. Use a scan tool in order to clear the DTCs.
  2. Start the engine and idle at normal operating temperature.
  3. Operate the vehicle within the conditions for setting this DTC as supported in the text.

Does the scan tool indicate that this diagnostic ran and passed?

Go to Step 8

Go to Step 2

8

Check if any additional DTCs are set.

Are any DTCs displayed that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK