P134B Buick the main thing to check is to verify the operation of the VCT solenoid. You're looking for a sticking or stuck VCt solenoid valve caused by contamination. Refer to vehicle specific repair manual to perform component tests for the VCT unit.
Remove the air filter box assembly so you can access the transmission range switch. Turn the key to the ON position, but do not start the vehicle. Move the shifter to the neutral position. Align the alignment holes between the switch and the shift lever. Insert a 5mm drill bit into the adjustment hole to verify the proper alignment for the neutral position.
Brake Switch Out of Self-Test Range Indicates that during Key On Engine Off (KOEO) Self-Test, BPP signal was high. Or during Key On Engine Running (KOER) Self -Test, the BPP signal did not cycle high and low. Open or short in (BPP) circuit Open or short in stoplamp circuits Damaged PCM Malfunction in module(s) connected to BPP circuit (Rear Electronic Module [REM] Windstar and LS6/LS8 and Lighting Control Module (LCM) Continental and Town Car) Damaged Brake Switch Misadjusted Brake Switch Check for proper function of stoplamps. Follow correct Self-Test procedures, refer to Section 2, Quick Test.
P134B meaning and repair processes are the same for all Buick models.
P134B Buick Trouble Repair Process:
If your vehicle failed a P134B Buick test and the P134B Buick Check Engine Light is NOT on, chances are you have a problem with the OBDII system, a burned out MIL lamp, or a faulty catalytic converter. The converter is essentially an afterburner that cleans up the exhaust after it exits the engine. The OBDII system uses a ownstream oxygen sensor to monitor the efficiency of the converter, and it should detect a drop in converter efficiency if the converter has been contaminated or is failing (ignition misfiring, leaky exhaust valves, and oil burning can all damage the converter). What you want to look any conditions that might cause ignition misfire, an overly rich or lean fuel condition, or loss of compression. Use your OBD Express DIY to look at the oxygen sensor outputs, coolant temperature, airflow, calculated engine load, and inlet air temperature.
On 1999 and later P134B Buick engines, the instrument cluster has a built-in self-diagnostic mode that can be accessed by pressing and holding the instrument cluster SELECT/RESET button. Insert the ignition key and turn to the RUN position (but don't crank or start engine). Continue to press and hold the SELECT/RESET button (for 5 seconds) until the word TEST is displayed by the odometer. Release the SELECT/RESET button within three seconds after the word TEST is displayed to begin the self-diagnostic mode.