Circuit Description
The Vehicle Theft Deterrent (VTD) system consists of the following components:
| • | Powertrain control module (PCM) |
| • | Powertrain interface module (PIM) |
| • | Body control module (BCM) |
| • | Remote receiver module |
After the BCM has confirmed the correct key has been used, the BCM sends a password to the PIM via the UART Serial Data circuit. The PIM will operate the starter motor, and supply another password via Class 2 Serial Data to the PCM. When this password matches the password stored in the PCM, the system enables the fuel injection.
If the BCM does not send a password or if the PCM does not receive it, the vehicle will not start unless the PCM is in VTD Fail-Enable mode. If the BCM and PCM lose communications with each other after the system has received the correct password, the PCM goes into VTD Fail-Enable mode. This allows the driver to restart the vehicle on future ignition cycles until communications between the BCM and PCM are restored. If the BCM and PCM lose communication before the PCM receives the BCM password, the PCM disables the fuel injection until communication is restored to prevent vehicle theft. In both cases DTC P1626 sets, which is a type C DTC. The PCM will not disable the fuel injection once the PCM enables the fuel within a given ignition cycle to prevent stalling as a result of theft deterrent system faults.
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
| • | The system has reached fuel enable decision point. |
| • | The PCM is in Fail Enable Mode due to loss of communication with the PIM after the system received the correct password earlier in the ignition cycle. |
| • | The PCM does not receive the password message from the PIM prior to the theft deterrent Fuel Decision Point. |
Action Taken When the DTC Sets
| • | The PCM stores the DTC information into memory when the diagnostic runs and fails. |
| • | The Check Powertrain malfunction indicator lamp (MIL) will not be activated. |
| • | The PCM records the operating conditions at the time the diagnostic fails. |
| • | The PCM stores this information in the Failure Records. |
| • | The multifunction display (MFD) in the instrument will display a message at key-on and key-off. |
Conditions for Clearing the MIL/DTC
| • | A Last Test Failed (current DTC), clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
| • | Use Tech 2 to clear the DTC. |
Diagnostic Aids
The most likely cause of DTC P1626 is a loss of serial data communication from the PIM to PCM. Check for a loss of power or ground to the PIM or for other causes of communication loss. Check for the following:
| • | Open Class 2 circuit |
| • | Grounded Class 2 circuit |
| • | Shorted to voltage Class 2 circuit |
| • | PIM ignition feed fault |
| • | PIM ground fault |
If there is a problem on the Class 2 circuit, the PIM should set a DTC U1000 or DTC U1001, B2006. Always check for this DTC when P1626 is set. Using the Failure Records data may aid in locating an intermittent condition. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass and/or fail. Operate the vehicle within the same Failure Records condition (RPM, load, vehicle speed, temperature etc.) that you observed. This will isolate when the DTC failed. For an intermittent, refer to Testing for Intermittent Conditions and Poor Connections
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
An engine that does not start and a DTC P1626 that is set, indicates that there is a Class 2 Serial Data circuit problem. There may be several PIM DTCs set if the Class 2I Serial Data circuit has malfunctioned.
-
If both PCM DTCs P1626 and P1630 are set, check for a fault with either the PIM power feed or PIM ground circuits.
-
An engine that does not crank indicates there is a problem with the BCM or the PCM. If a BCM or PIM DTCs are set, refer to that DTC for diagnosis
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Theft Deterrent System Schematics | |||
1 | Was the Diagnostic System Check - Engine Controls performed? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls in Engine Controls |
Crank the engine. Does the engine crank and run? | Go to Step 9 | Go to Step 3 | |
Using Tech 2, inspect for PCM DTC P1626, and P1630. If DTC P1630 is set, the PCM/PIM/BCM linking procedure must be completed. Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control System. Are any PCM DTCs Set? | Go to Step 5 | Go to Step 4 | |
Are any powertrain interface module (PIM) DTCs set? | Go to Diagnostic Trouble Code (DTC) List in Data Link Communications | Go to Step 7 | |
5 |
Was a problem found? | Go to Step 9 | Go to Step 6 |
6 | Replace the PIM. Refer to Body Control Module (BCM) Programming/RPO Configuration in Body Control System. Is action complete? | Go to Step 9 | -- |
7 | Inspect for poor connection in Class 2 Serial Data circuit from powertrain control module (PCM) to PIM. Was a poor connection found? | Go to Step 8 | Go to Step 9 |
8 | Repair the open, short to ground, or short to voltage in Class 2 Serial Data circuit. Is action complete? | Go to Step 9 | -- |
9 |
Does Tech 2 indicate that this DTC reset? | Go to Step 2 | System OK |
