Cold Start Stall, False DTC's 31, 55, and 56 Set
90pontiac09Bulletin Number: 90-6-31
Reference Number: 036508
Publish Date: 5/90
Subject: COLD START STALL (SETTING FALSE CODES 31, 55 AND 56 AND MASKED 46) (NEW MEMCAL)
Models
Affected: 1990 FIREBIRD WITH 3.1L AND A/T
CONDITION: Customers may experience cold start stall and/or dealer service may find false Codes 31, 55, and 56 while trying to diagnose the vehicle for various conditions. Also, the VATS system code 46 may not be set.
CAUSE: System component variability plus low fuel volatility.
CORRECTION: If any of the subject conditions are found, then complete the following procedure:
1. Perform diagnostics, per Section 6E of the Service Manual. Make any adjustments as required, or replace any defective parts.
2 . If no other conditions were found using normal diagnostics, and
the condition or conditions still exist, then replace the MEM-CAL with one from the following table:
Part Number Description Code
16150975 MEM-CAL (Fed.) AUJW
* 16150981 MEM-CAL (Calif.) AUJX
3. (A) Pull the underhood ECM continuous power fuse or disconnect the battery and leave it disconnected for at least 10 minutes.
(B) Remove current MEM-CAL and install a new service MEM-CAL.
(C) Restore the battery power and place air conditioning controls (if equipped) in the "off" position.
(D) Firmly apply the parking brake and block the drive wheels. Start the engine, and shift the transmission to "drive".
(E) Allow the engine to run until the engine cooling fan has cycled once, or a maximum of 10 minutes.
(F) Turn the ignition key to the off" position for at least 5 seconds.
(G) Start the engine, and shift the transmission to "drive".
(H) Allow engine to run for at least 5 minutes.
* Parts are currently available from GMSPO.
Labor Operation Number: T1619
Labor Time : 0.8 Hours