PCM - Light Spark Knock Condition: Overview
NO: 18-24-98GROUP: Vehicle Performance
DATE: Jul. 31, 1998
SUBJECT:
Light Spark Knock
Timing Retard Feature
MODELS:
1996 - 1997 (AB) Ram Van
1996 - 1997 (AN) Dakota
1996 - 1997 (BR) Ram Truck
1996 - 1997 (XJ) Cherokee
1996 - 1997 (ZJ) GrandCherokee
1996 - 1997 (ZG) Grand Cherokee (International Markets)
NOTE:
THIS INFORMATION APPLIES TO VEHICLES EOUIPPED WITH A 2.5L, 4.OL, 3.9L, 5.2L AND 5.9L LIGHT DUTY GASOLINE ENGINES.
SYMPTOM/CONDITION:
Some vehicles may exhibit light spark knock with a warm engine under load.
DISCUSSION:
Determine when the customer exhibits this condition and verify it by driving the vehicle in similar conditions. If the vehicle exhibits light spark knock with a warm engine under load perform the flash update procedure. Once the flash procedure is completed, spark advance/retard may be adjusted.
NOTE:
THE DRB III(R) MUST BE OPERATING AT RELEASE 25.5 OR HIGHER.
Select DRB III(R) stand alone, current model year diagnostics, engine, and miscellaneous. When in miscellaneous, spark advance will be available. Use the arrow keys to retard timing in 20 increments to a maximum of A°. When the DRB III(R) screen reads 0 the vehicle will be set at maximum advance and when at -4 it will be set at maximum retard.
NOTE:
THE IGNITION KEY MUST BE CYCLED FOR THE CHANGES TO TAKE EFFECT.
After performing the spark advance/retard feature, drive the vehicle to verify that the light spark knock is gone.
This feature will not compensate for heavy spark knock conditions. If heavy knock is experienced, funher diagnosis and testing will be required.
NOTE:
WHENEVER A POWERTRAIN CONTROL MODULE (PCM) IS REPLACED DUE TO FAILURE, THE SOFTWARE OF THE REPLACEMENT CONTROLLER SHOULD BE VERIFIED FOR THE LATEST REVISION LEVEL. USE THE FLASH PROCEDURE TO UPDATE REPLACED CONTROLLERS AS NECESSARY.
EQUIPMENT/PARTS REQUIRED:
1 CH6OOO ScanTool (DRBIII(R))
1 CH7035 General Purpose Interface Bus Cable (GPIB)
1 CH7OOO/7001 J1962 Cable
1 04669020 Label - Authorized Software Update
1 04275086 Label - Authorized Modification
NOTE:
THE MDS AND DRB III(R) ARE REQUIRED TO PERFORM THIS REPAIR AND THE SYSTEM MUST BE OPERATING WITH RELEASE 21 OR HIGHER AND TIL CD RELEASE 1165 OR HIGHER MUST BE INSTALLED. THE DRB III(R) MUST BE OPERATING AT RELEASE 25.5 OR HIGHER.
POLICY: Reimbursable within the provisions of the warranty.
TIME ALLOWANCE:
Labor Operation No: 08-19-41-96 0.5 Hrs.
FAILURE CODE: FM - Flash Module