B2722

DTC B2722 Pass-Key (R) II Detention Circuit Shorted To Ground:

DTC B2722 Pass-Key (R) II Detection Circuit Shorted To Ground (Part 1 Of 2):

DTC B2722 Pass-Key (R) II Detection Circuit Shorted To Ground (Part 2 Of 2):

CIRCUIT DESCRIPTION
The Personal Automotive Security System (PASS-Key(R) II) is a vehicle theft deterrent system. The PASS-Key(R) II is designed to prevent vehicle theft by disabling the engine from starting unless an ignition key with a specific resistor pellet code is used in the ignition lock cylinder.

The ignition lock cylinder contains the resistor sensing contacts. These contacts touch the resistor pellet embedded in the ignition key. When the ignition key is inserted in the ignition lock cylinder, the resistor pellet completes the key detection circuit (circuits 1073 and 1074).

When the ignition switch is turned from the LOCK or OFF to the RUN position, the Body Control Module (BCM) applies a 5V reference voltage to circuit 1073. Then, the BCM reads the resistor pellet code and compares the stored resistor pellet code against the ignition key resistor pellet code for a correct match.

Upon detecting a correct match, the BCM sends a fuel enable password to the Powertrain Control Module (PCM) through the Class II serial data link. As a result, the PCM enables the theft deterrent relay, and allows fuel delivery to the engine.

CONDITIONS FOR SETTING THE DTC
^ The voltage detected in circuit 1073 by the BCM is low, indicating that a short to ground is present.
^ Condition must be present during an engine start attempt, or for 1 second anytime after the engine has started.

ACTION TAKEN WHEN THE DTC SETS
^ The BCM stores DTC B2722 in memory.
^ The BCM sends a message to the Instrument Panel Cluster (IPC) to turn on the SECURITY indicator through the Class II serial data link.
^ In addition, the BCM takes one of two actions:
A. If circuit 1073 is shorted to ground when attempting to start the engine, the BCM will NOT send a message to the PCM to enable the theft deterrent relay, and to deliver fuel to the engine. The vehicle will exhibit an engine no crank condition, OR
B. If circuit 1073 is shorted to ground after the engine has started, the BCM enters a fail-enable mode. Upon subsequent engine start attempts, the BCM will send a password message to the PCM via the Class II serial data link to enable the theft deterrent relay, and to deliver fuel to the engine. The engine will start.

CONDITIONS FOR CLEARING THE DTC
^ A current DTC B2722 clears when the BCM detects a valid PASS-Key(R) II resistance value on the PASS-Key(R) II input circuit (circuit 1073).
^ A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
^ Using a scan tool.

DIAGNOSTIC AIDS
^ Check for a short between circuit 1073 and circuit 1074, or a short to ground in circuit 1073.
^ The following conditions may cause an intermittent malfunction to occur:
- Shorted key resistor pellet.
- Shorted ignition key cylinder contacts.
- An intermittent short to ground in circuit 1073.
- An intermittent short between circuit 1073 and circuit 1074; the BCM would interpret this as a short to ground condition.
^ If the DTC is a history DTC, the problem may be intermittent. Try performing the tests shown while moving wiring, connectors, and the key, this can often cause the malfunction to appear.
^ DTC P1626 will set in the Powertrain Control Module (PCM) when the ignition switch is in the RUN position with the BCM disconnected. When BCM diagnostics and repairs are completed, refer to the Engine Controls for additional information on PCM related DTCs. Powertrain Management

TEST DESCRIPTION
Numbers below refer to the Step numbers on the diagnostic table.
2. Checks if the PASS-Key(R) II resistor pellet is within the allowable range.
3. Checks for a short to ground on the ignition lock cylinder and its pigtail circuit.
4. Checks for a short to ground in circuit 1073.
5. Checks for a short between circuit 1073 and circuit 1074, which the BCM would interpret this as a short to ground.
6. Determines whether the malfunction is intermittent or the BCM is faulty.