P1626

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

The Class II serial date circuit is used to communicate between the Vehicle Control Module (VCM) and the Vehicle Theft Deterrent System (VTD) (Passlock)/Electronic Variable Orifice (EVO) Control Module systems.

The VTD sends a Vehicle Security Password when its ignition 1 input becomes active and includes its source ID. The Vehicle Security Password includes either a Fuel Continue or a Fuel Disable Password. When the Passlock portion of the Vehicle Theft Deterrent System (VTD) system has sensed the proper operation of the ignition switch and lock (switch and lock are not tampered with), the Passlock system transmits a password to the VCM. The VCM enables fuel delivery if this password matches the password stored in the VCM's memory. However; if communication is lost or a VTD failure occurs (during an ignition cycle that the VCM has enabled fuel) the VCM will enter a fail-safe mode: Fail Enable (VTD System Failure with Fuel Enabled). The VCM remains in Fail Enable mode, for the current and future ignition cycles, until the fault is corrected and a valid pass word is received, or until battery power is removed. If the battery power is removed while the VCM is in the Fail Enable mode (ignition ON or OFF) the VCM disables fuel delivery. The vehicle will not start, or it will start then stall.

When the VCM receives an invalid password or no password, before the Fuel Disable Decision Point, the VCM disables fuel delivery. The Fuel Disable Decision Point occurs at about 300 RPM during the engine crank mode.

CONDITIONS FOR SETTING THE DTC

^ The VCM has established communications and received the Vehicle Security Password during the current ignition cycle from the VTD (Passlock) Control Module.

^ The VCM has not detected communications and/or has not received Node Alive/State of Health (SOH) messages from the VTD (Passlock) Control Module for 5 seconds.

^ OR

^ The VCM cannot establish communications with the VTD (Passlock) Control Module and has not received a valid password before the Fuel Disable Decision Point.

ACTION TAKEN WHEN THE DTC SETS

When the failure occurs after the VCM enables fuel due to the receipt of a Vehicle Security Password containing the Fuel Continue Password:

^ The vehicle starts.

^ The VCM continues to enable fuel delivery (Fuel Enabled after Security Fault mode), until the fault is corrected and a valid password is received from the VTD (Passlock) Control Module. If the fault is corrected and a valid password is received, fuel delivery is enabled. The difference is that the Fail Enable Active bit in the Vehicle Security Status message will now be false while the Fuel Continue State bit will be true.

^ A DTC P1626 is stored in the VCM memory.

^ The VCM will not illuminate the Malfunction Indicator Lamp (MIL). When the failure occurs during ignition OFF, or before the VCM receives a valid Passlock password during engine cranking (about 300 RPM).

^ The vehicle does not start; or it starts and stalls.

^ The VCM disables fuel delivery, until the fault is corrected and a valid password is received from the VTD (Passlock) Control Module.

^ A DTC P1626 is stored in the VCM memory.

^ The VCM will not illuminate the MIL.

CONDITIONS FOR CLEARING THE MIL/DTC

^ A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22°C (40°F) from the start-up coolant temperature and the engine coolant temperature exceeds 70°C (160°F) during the same ignition cycle.

^ Use the scan tool Clear Information function.

^ Disconnect the VCM battery feed for 30 seconds.

DIAGNOSTIC AIDS

IMPORTANT: Do not clear DTCs unless directed by a diagnostic procedure. Clearing DTCs will also clear valuable Freeze Frame and Failure Records data.

^ Check for published service bulletins relating to exhibited symptoms or component operation.

^ Inspect all related wiring and connections including the VCM and VTD (Passlock) Control Module connections. These may cause an intermittent malfunction.

^ Thoroughly check any circuit that can cause an intermittent complaint for the following:

- Backed out terminals.

- Improper mating.

- Broken locks.

- Improperly formed or damaged terminals.

- Poor terminal to wiring connections.

- Physical damage to the wiring harness.

- Corrosion.

^ If the serial data line is shorted to ground or shorted to voltage, then all systems connected to the serial data line will not be able to communicate properly. Systems capable of storing loss of communications DTCs (DTCs with the letter U as a prefix) will have these codes stored in their memory. If a DTC P1626 is stored in VCM memory, then check for the same DTC stored in the Active Transfer Case (ACT) Control Module. The Active Transfer Case (ATC) Control Module also monitors the Node Alive/State of Health (SOH) message from the VTD (Passlock) Control Module. If the Active Transfer Case (ATC) Control Module also has a DTC 1626 stored, check the VTD (Passlock) Control Module for an intermittent malfunction. If the ATC Control Module does not have a DTC P1626 stored, then check for an open in the serial data line between only the VCM and the VTD (Passlock) Control module. The VCM must also be checked for intermittent operation due to a loss of power or ground to the VCM itself. After repairing the cause of DTC P1626, clear all DTCs from all systems capable of storing this DTC.

^ If the vehicle does not start, or starts and stalls:

- Turn OFF the ignition and wait at least 5 seconds before trying to restart.

- When the VCM receives a password from the VTD (Passlock) Control Module that does not match the stored password, a DTC P1631 should be present. Check for VTD codes first; if no codes are present, then force a relearn of the password.

- If both a VCM DTC P1626 and U1192 are set, check the wiring between the VCM and VTD (Passlock) for continuity.

- If a VCM P1626 code is set, but a VCM DTC U1192 is not, then the VTD (Passlock) Control Module may be malfunctioning.

- If VCM DTCs P1526, P1630, P1631, U1192 are not set, the cause of the no start is probably not a VTD (Passlock) system problem.

^ Monitor the VCM's VTD (Passlock) parameters with a scan tool.

^ The scan tool's Diagnostic Circuit Check can be used to:

- Monitor the Class II Serial Data circuit for modules which have been or are communicating.

- Monitor for loss of communications DTCs (DTCs with the letter U as a prefix: U1001-Ui199).

- Clear loss of communications DTCs. When a Clear Codes command is issued, all codes, freeze frame, and failure records information is cleared.

^ The scan tool's Diagnostic Circuit Check's Active status indicates that the module is communicating with the scan tool; Inactive indicates that a module that had established communications with the scan tool is not currently communicating. If a module is not listed at all, then the missing module never successfully established communications with the scan tool; refer to Diagrams for any unlisted modules.

TEST DESCRIPTION

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

2. This test checks if communications can be established between the scan tool and the Electronic Brake Control Module (EBCM).

3. This test determines if DTC P1626 is set due to a loss of communications with the VCM or the EBCM. The ATC Control Module also communicates with the EBCM. If a DTC P1626 is stored in the ATC Control Module memory, the EBCM must be diagnosed first.

4. This test checks for any opens in the serial data circuit between the VCM and the EBCM. It also checks for any intermittent malfunctions associated with the serial data line.

8. Use a scan tool to clear and check for any DTCs in all the modules connected to the Class II Serial Data circuit (VCM, ATC, and EBCM).