For 1990-2009 cars
Engine Controls Components
Engine Controls Schematics
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The Vehicle Theft Deterrent system is incorporated within the Body Control Module (BCM). The PCM monitors the state of heal the serial data message from the theft deterrent system to ensure that the PCM-BCM communications is established. If the PCM detects a loss of the state of health message while the engine is running, DTC P 1626 will be set. DTC P1626 can cause a no start condition or normal operation depending on when the loss of communication was detected. The engine will continue to start and run if the condition that set DTC P1626 occurred after the PCM received a valid theft deterrent password from the BCM and already allowed fuel during the ignition cycle. The engine will start and immediately stall if the condition that set the DTC occurred before the PCM received a valid theft deterrent password. With this condition present, the PCM will inhibit fuel delivery and disable the starter until a valid theft deterrent password is detected.

### Conditions for Setting the DTC

The PCM cannot communicate with the theft deterrent system.

### Action Taken When the DTC Sets

The PCM stores conditions which were present when the DTC set as Failure Records only. This information will not be stored as Freeze Frame Records.

### Conditions for Clearing the MIL/DTC

• | The DTC becomes history when the conditions for setting the DTC are no longer present.

• | The history DTC clears after 40 malfunction free warm-up cycles.

• | The PCM receives a clear code command from the scan tool.

### Diagnostic Aids

Attempting to start the vehicle by bypassing the theft deterrent system or substituting parts without performing the password learn procedure may set a DTC P1631.

If no password is received a DTC P1610, and P1631 may also be set.

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.

Any circuitry, that is suspected as causing an intermittent complaint, should be thoroughly checked for the following items:

• | Backed out terminals or improper mating.

• | Broken locks.

• | Improperly formed or damaged terminals.

• | Poor terminal to wiring connections.

• | Physical damage to the wiring harness.

• | Corrosion.

If the Body Control Module (BCM) is replaced, the PCM must be reflashed to allow the new password to be learned. The ignition must be turned off for at least 30 seconds then on for the PCM to learn the new BCM password.

### Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table:

1. The Powertrain OBD 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 fault occurred. The information is then stored in the scan tool for later reference.

2. A scan tool that cannot display PCM data indicates that a short exists on the serial data circuit.

3. The replacement PCM must be reprogrammed and the crankshaft position system variation procedure must be performed.

   If the serial data loss occurred after a good theft password has been received, the PCM must be reprogrammed and the password learn and the crankshaft position variation learn procedures must be completed to allow the theft system to operate properly. Refer to Powertrain Control Module Replacement/Programming , Crankshaft Position System Variation Learn and Password Learn Procedure for reprogramming procedures.

4. If the serial data circuit to the Body Control Module (BCM) was not open, then the serial communication loss to the PCM lies within the BCM. Refer to Body Control Module portion of the service manual for Passlock diagnosis.

5. If no malfunctions have been found at this point and no additional DTCs were set, refer to Diagnostic Aids for additional checks and information.

#### DTC P1626 - No Password Received from Body Control Module (BCM)

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain ON Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Install a scan tool. Was DTC P1610 also set? | -- | GO to DTC P1610 Class II Failure with BFC | Go to Step 3
3 | Has any part of the vehicle theft deterrent system been tampered with? | -- | Go to Step 4 | Go to Step 5
4 | Repair tampered component. Perform the Passlock learn procedure. Refer to Password Learn . Is the action complete? | -- | Go to Step 8 | --
5 | Momentarily rotate the ignition cylinder to crank without starting the vehicle. Does the BCM indicate the password is valid? | -- | Go to Step 6 | Go to Step 7
6 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | Go to Step 8 | --
7 | Check for BCM DTCs and make any necessary repairs. Is the action complete? | -- | Go to Step 8 |
8 |

1. Using the scan tool, clear DTCs.
2. Start engine and idle at normal operating temperature.
3. Operate vehicle within the conditions for setting this DTC as specified in the supporting text.

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

--

Go to Step 9

Go to Step 2

9 | Check if any additional DTCs are set. Are any DTCs displayed that have not been diagnosed? | -- | Go to the applicable DTC | System OK