PIP4828B

File in Section:
Service Bulletin
Bulletin No.:
Date:
PIP4828B
January, 2013
PRELIMINARY INFORMATION
Subject:
Rough Idle And/Or Lack Of Power On Acceleration After Cold Start - Possible
Characteristic
Models:
2009-2013 Chevrolet Express, Silverado, Suburban
2009-2013 GMC Savana, Sierra
With any of the following V8 Engine RPO Codes:
6.0L - L76, L77, L96, LY6
6.2L- L94 L9H
This PI was superseded to update recommended field. Please discard PIP4828A.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern
Some customers may complain of a rough idle and/or momentary lack of power after cold starting the engine and
immediately placing the transmission in gear. This concern will diminish within a couple minutes of start up as the
engine warms up. Upon inspection, no DTCs will be stored and all scan data will appear normal as well.
This may be a characteristic of the ECM calibration. The ECM calibration is designed to meet cold start emissions
without the use of an AIR pump by retarding the timing to warm up the catalytic converter. Unfortunately, this may
affect cold start drivability is some cases.
Recommendation/Instructions
If SI diagnosis does not isolate the cause of this concern and all of the following statements apply, this should be
considered a characteristic of the ECM calibration and no additional repairs should be performed:
1. The concern has been present since the vehicle was new.
2. The concern is greatly improved or eliminated if the engine is allowed to warm up for 2 minutes or more.
3. The concern is present on a similarly equipped vehicle.
4. The concern is still present when using one of the top-tier gasoline’s listed in the latest version of 04-06-04-047
(US) or 05-06-04-022 (Canada). Unless premium fuel is required, 87 octane should be used to get the best cold
drivability performance.
5. There are no DTCs present.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is
resolved without completing every step, the remaining steps do not need to be performed.