Computer Relearn Procedures Buick Roadmaster VIII

Vehicles equipped with engine or transmission computers may require a relearn procedure after the vehicle battery is disconnected. Vehicle computers memorize and store vehicle operation patterns for optimum driveability and performance. When the vehicle battery is disconnected, this memory is lost. Default data is used until new data from each key start is stored. As the computer restores its memory from each new key start, driveability is restored.

Driveability problems may occur during the relearn stage. Depending on the vehicle and how it is equipped, the following driveability problems may exist

1. Rough or unstable idle.
2. Hesitation or stumble.
3. Rich or lean running.
4. Poor fuel mileage.
5. Harsh or poor transmission shift quality.

To accelerate relearn process after battery removal and installation, vehicle should be road tested in the following manner

1. Vehicle at normal operating temperature (cooling fan cycles).
2. Accelerate at normal throttle position (20-50%).
3. Cruise at light to medium throttle.
4. Decelerate to a stop, downshifting and using brakes normally.

Manufacturers identify specific relearn procedures. See SPECIFIC RELEARN PROCEDURES. Always complete the procedure before returning the vehicle to the customer.

TPS and throttle angle relearn are necessary whenever battery is disconnected, TPS is disconnected or Code E052 or E52 is set. Because of engine load differences, idle relearn must occur with A/C both on and off.

TPS - Idle Relearn routine is used in the PCM software to compensate for changes in closed throttle TPS adjustment and air flow through the throttle body during coastdown. These variations can be caused by carbon deposits on the throttle valves. The Idle Learn routine differs from the TPS Learn capability of the PCM. TPS Learn is performed by the PCM with the engine OFF. Idle Learn is performed with the engine running and when specific operating conditions have been met.

The TPS Learn routine provides a closed, or base, throttle angle that is used as a zero point for all throttle angle calculations. The Idle Learn routine provides a particular idle throttle angle offset, determined by throttle body condition, that is added to all coastdown throttle angles. Whenever the battery has been disconnected, the closed throttle angle is set to zero and the idle throttle angle offset is set to a specific, calibrated value. When the battery is reconnected, and the vehicle driven, these initial offsets could be too high or too low. Improper throttle angle can result in a coastdown "sail-on" condition or an engine stall. Performing the following TPS/Idle Learn procedure lets the PCM learn the proper closed throttle angle and throttle angle offset for the particular throttle body

1. All service procedures must be complete. Reset minimum air, TPS and max ISC extend, if necessary.
2. Warm engine until operating temperature is reached. Coolant temperature must be greater than 176°F (80°C). This takes approximately 8 minutes (Up to 18 minutes on Allante).
3. Enter diagnostics. Turn ignition off. Allow approximately 20 seconds for the ISC motor to retract and perform a TPS learn.
4. Repeat Step 3).
5. Allow engine to idle in PARK with wheels straight ahead for at least 5 minutes, ensure coolant temperature is greater than 176°F (80°C).
6. With brake applied and Climate Control in the OFF position, place the transmission in "D" position and allow the engine to idle (foot off accelerator) for at least one minute.
7. Ensure outside air temperature reading is at least 50°F. While still in "D", with brakes applied and at idle, place Climate Control in the AUTO position and verify A/C clutch engagement. Allow engine to idle for at least one minute. CAUTION: Because of the load differences on the engine with A/C ON versus OFF, it is VERY IMPORTANT that learning be procedure be performed under both conditions.
8. Place transmission in PARK and turn engine OFF.

THROTTLE POSITION SENSOR RELEARN (1993 CORVETTE)

If a NEW TPS or throttle body is installed, EBCM must learn new TPS idle position voltage. This procedure is necessary to ensure effective engine torque reduction during ASR operations. TPS learn procedure requires a Tech 1 scan tester or T-100 (CAMS) unit.

1. Turn ignition off. Connect Tech 1 scan tester with a Mass Storage or Chassis Cartridge. Turn ignition on. Select ABS/ASR feature from menu.
2. Select F5: TP SENSR LEARN. Press up arrow to begin learn procedure. Wait for Tech 1 scan tester to indicate COMPLETE. Turn ignition off. Disconnect Tech 1 scan tester.

IDLE LEARN PROCEDURE (3.1L & 3.4L)

Any time the battery is disconnected, the programmed position of the IAC valve pintle is lost, and replaced with a "default" value. To return the IAC valve pintle to the correct position, perform the following procedure

Note. This procedure, called the "quick-learn" Idle Learn procedure, utilized the capabilities of the Tech 1 "Scan" tool. For the procedure to work properly, the vehicle transaxle must be in Park or Neutral.

1. Restore battery power and place transaxle in Park or Neutral. Connect Tech 1, "Scan" tool. Select "IAC" System," then select "Idle Learn" in the "Misc. Test" mode.
2. Proceed with idle learn as directed.

This procedure allows the ECM memory to be updated with the correct pintle position for the vehicle, and provide a stable idle speed.