Service Procedure

1. Perform diagnostic procedures per Section 6E of the Service Manual, and correct any faults except for Codes 33, 34, 23 or 25. If the diagnostics indicate the Mass Air Flow (MAF) is to be replaced or a Code 33 or 34 is present, DO NOT REPLACE THE MAF SENSOR! Proceed to Step # 3. If a Code 23 or 25 is present, go to Step # 2 below. PROCEED TO STEP # 3 ONLY IF NORMAL DIAGNOSTIC CHECKS DID NOT IDENTIFY A CAUSE FOR THE CUSTOMER CONCERN.


2. If a Code 23 or 25 is stored, perform the model year diagnostics for the Manifold Air Temperature Sensor (MAT). If the diagnostics indicate that the MAT is faulty and replacement is required, replace the combination MAT/MAF sensor. Proceed to Step # 3.


3. Install a new MEM-CAL into the Engine Control Module (ECM) per instructions below. The new MEM-CAL is available from GMSPO. See attached service part number chart. Install the identification label package to the ECM access door and to the left shock tower per label kit, P/N 10154725 instructions.


IMPORTANT: The new MEM-CAL to be installed does not need or use the existing MAF signal; however, it does need and use the MAT signal.

A). Pull the underhood ECM continuous power fuse or disconnect the battery and

leave it disconnected for at least 10 minutes.

B). Remove MAF relay, if applicable, and discard. Tape up connector to prevent

water intrusion.

C). Remove current MEM-CAL and install a new service MEM-CAL.

D). Restore the battery power and place air conditioning controls (if equipped) in

the "off" position.

E). Firmly apply the parking brake and block the drive wheels. Start the engine,
and shift the transaxle to "drive" for automatics or "neutral" for manuals.

F). Allow the engine to run until the engine cooling fan has cycled once, or a
maximum of 10 minutes.

G). Turn the ignition key to the "off" position for at least 5 seconds.

H). Start the engine, and shift the transaxle to "drive" for automatics or "neutral" for manuals.

I). Allow engine to run for at least 5 minutes.


After a MEM-CAL replacement, the 1987-88 2.8L speed density service diagnostics supplement must be used for driveability and emissions diagnostics. Until the supplement is available, use 1989 model year for scanner-type diagnostics. For additional information, call the GM Technical Assistance Network.


Use applicable labor operations and times.


Labor Operation Number: J5670 for MAF/MAT replacement


Labor Operation Number: T1492 for repair procedures in step 3.


A-Car 1.0 Hour

J-Car 0.9 Hour

1987 L-Car and 1988 L-Car prior to Vin sequence 500,000 = 0.9 Hour


1988 L-Car (After Vin sequence 500,000) = 0.8 Hour