PCM - Cold Start Sag/Hesitation or Backfire/Pop
NO: 18-23-95GROUP: Vehicle Performance
DATE: Jun. 30, 1995
SUBJECT:
Cold Start Sag/Hesitation and/or Exhaust Backfire or Pop
MODELS:
1994 - 1995 (AB) Ram Van/Wagon
1994 - 1995 (AN) Dakota
1994 - 1995 (BR) Ram Truck
NOTE:
THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH A 3.9L ENGINE.
SYMPTOM/CONDITION:
^ Driving away after a cold start up, a sag/hesitation may be experienced. At idle, a slight engine surge/rough idle may also be felt. The condition may persist for up to one minute and be most prevalent on cold starts at ambient of 60-80 degrees F.
^ An exhaust backfire or popping noise in the exhaust system may occur during a closed throttle deceleration before the engine has reached normal operating temperatures.
^ The vehicle may exhibit one or both of these conditions.
DIAGNOSIS:
Using the Mopar Diagnostic System (MDS) or Scan Tool (DRB III) with the appropriate Diagnostic Procedure Manual, verify that all engine/transmission systems are functioning as designed. If Diagnostic Trouble Codes (DTC's) are present, record them on the repair order and repair before proceeding with the repair procedure in this bulletin.
COLD START SAG/HESITATION:
1. Allow engine to cool down at least eight (8) hours, preferably overnight.
2. Following cold start drive away, make frequent stops and medium accelerations checking for sags and hesitations. If sags or hesitations result, perform the repair procedure.
EXHAUST BACKFIRE OR POPPING NOISE:
1. While vehicle is still cold, start engine and accelerate in first gear until engine speed reaches 3000 RPM.
2. Remove foot from accelerator pedal. Decelerate the vehicle and allow the vehicle to come to a stop.
3. If a backfire or popping sound comes from the exhaust system during deceleration, perform the repair procedure.
PARTS REQUIRED:
1 4798341 POM, 3.9L Man. Trans AN Body 1994 MY
1 4798342 POM, 3.9L Auto Trans. AN Body 1994 MY
1 4798343 POM, 3.9L Auto Trans. AB Body 1994 MY
1 4798344 POM, 3.9L Man. Trans. BR Body 1994 MY
1 4798345 PCM, 3.9L Auto Trans. BR Body 1994 MY
1 4275086 Label - Authorized Modification
1 4669020 Label - Authorized Software Update
EQUIPMENT NEEDED:
1 CH6OOO Scan Tool (DRB III)
1 CH7035 General Purpose Interface Bus Cable (GPIB)
1 CH7015 Engine Cable
REPAIR PROCEDURE:
This bulletin includes the replacement of the Powertrain Control Module (PCM) for 1994 model year vehicles, and the flashing of 1995 model year vehicles with revised software.
MODULE REPLACEMENT:
This section of the bulletin involves the replacement of the powertrain control module with one of the above powertrain control modules.
1. Record all radio station presets.
2. Disconnect negative cable at battery and isolate.
3. Remove 60 way electrical connector from POM (one bolt). POM is located in the right rear side of the engine compartment.
4. Remove the three PCM mounting bolts and remove PCM.
5. Install new PCM and torque bolts to 9 in. lbs. (1 Nm) torque.
6. Connect 60 way electrical connector to POM. Torque bolt to 35 in. lbs. (4 Nm).
7. Connect negative cable to battery.
8. Program radio station presets and clock.
9. Proceed to module reprogramming.
1995 MODULE REPROGRAMMING:
This section of the bulletin involves reprogramming the PCM with new software and installation of appropriate labels.
NOTE:
THE MOPAR DIAGNOSTIC SYSTEM IS REQUIRED TO PERFORM THE FOLLOWING REPAIR. THE SYSTEM MUST BE OPERATING WITH RELEASE 16 OR LATER INSTALLED. (TIL CD 1083 OR LATER)
This repair involves selectively erasing and reprogramming the Powertrain Control Module with new software (calibration change).
1. Connect the MDS (Mopar Diagnostic System) and DRBIII (Scan Tool) to the vehicle and power them up.
2. Use the arrow keys and select # 2 MDS DIAGNOSTICS on the DRBIII MAIN MENU Screen.
3. Use the arrow keys and select DIAGNOSTIC MENU on the MDS, then press NEXT MENU.
4. Use the arrow keys and select CONTROLLER PROGRAMMING on the MDS, then press NEXT MENU.
5. Use the arrow keys and select PROGRAM CONTROLLER PART on the MDS, then press NEXT MENU.
6. Follow the steps presented on the MDS and DRBIII which will allow the DRBIII to obtain the current part number of the controller.
7. The MDS will display the part number of the controller on the vehicle and the appropriate replacement part number, then press NEXT MENU to begin programming.
If the controller on the vehicle has already been updated or programmed, a NO UPDATES AVAILABLE message will be displayed. Check the part number of the controller on the vehicle and compare it to the part number displayed. If the part numbers match and the controller update has been verified, proceed to Step 9.
8. The MDS and DRBIII will prompt for any operator action needed during the remainder of the programming process.
NOTE:
THE FOLLOWING STEPS ARE REQUIRED BY LAW.
Chrysler Authorized Software Update Label:
9. Type the necessary information on the "Authorized Software Update Label" and attach it to the PCM and cover the label with a clear plastic sticker.
Chrysler Authorized Modification Label:
10. Type the necessary information on the Authorized Modification Label and attach the label near the VECI Label.
POLICY:
Reimbursable within the provisions of the warranty.
TIME ALLOWANCE: Module. Powertrain Control Reprogram
Labor Operation No: 08-19-42-97 (1995 BR) 0.5 Hrs.
Replace Module. Powertrain Control and Reprogram
08-19-42-98 (1994 BR) 0.7 Hrs.
FAILURE CODE: FM - Flash Module