SB-10057674-6228
File in Section:

Service Bulletin

Bulletin No.:
Date:

PIP5172B
March, 2015

PRELIMINARY INFORMATION
Subject:

Police Tahoe Drivability Issues in Hot Weather with an Idle Surge, Sag or Stall

Models:

2012-2014 Chevrolet Tahoe Police Pursuit Vehicles (RPO code PPV) and Special
Service trucks (RPO code 5W4)
With engines 5.3L LMG

This PI was superseded to update Administrative Details. Please discard PIP5172A.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern
Customers may comment on an erratic idle, idle surge or sag, and other low engine speed drivability concerns,
including the potential for stall events that can occur infrequently.
These conditions are evident in hot weather especially after extended idle times.
This concern is on Tahoe Police Pursuit Vehicles (PPV) and Special Service Tahoe’s (5W4) and does not include
retail trucks.

Recommendation/Instructions
To correct the above concerns, update the following control module calibrations:
1. Engine Control Module calibration (Engine Operation) with a calibration in TIS2Web titled “New calibration to
address idle sag in high ambient temperatures” This can be completed through TIS
2. Regulated Voltage Control in the Body Control Module in the Charging/Energy Storage” category. This can be
completed through TIS.
Additional information to pass along to the operator of the vehicle and fleet management
Issues addressed with the updated calibration to minimize stall or idle surge events
1. Idle speed control modified to minimize idle surge/roll
2. Modified to reduce idle speed increase following most rolling stop maneuvers
3. Increased idle speed in high temperatures (650 rpm above 80F IAT) with A/C on
4. Modified purge vapor management
5. Maximize available spark advance for improved launch performance
Operational characteristics that are not addressed with the calibration
1. Some Idle roll/oscillation is inherent. Can occur on return to idle, but should stabilize/damp out quickly.
2. Uncompensated loads such as hydraulic power steering input can also disturb idle
3. A/C cycling may cause approx. 100 rpm idle speed variation for example from 650 to 550 rpm
4. Elevated idle – Trucks are equipped with idle boost strategy for various inputs (HVAC, electrical load…).
Level 1 – 650 RPM in drive / 800 RPM in park/neutral
Level 2 – 725 RPM in drive / 1000 in park/neutral
Level 3 – 800 RPM in drive / 1000 RPM in park/neutral.
Transmission shift points – The Tahoe PPV does have a performance oriented shift strategy, but can still experience
1. Some downshift delays in certain conditions.
2. Reverse to Drive transitions at too high of vehicle speed can result in stall and is considered an abusive
maneuver.
3. Low power in high ambient temperatures (should be improved by some small amount with updated calibration).

4. Lack of throttle response (tip-in/tip-out) – Known issue (anti-clunk) with no resolution - PIP4112N: Normal
Characteristic - Sag Or Hesitation On Acceleration.
5. Low power low speed acceleration – Known issue, trans shifting to lower gear delay, with no resolution PIP4112N: Normal Characteristic - Sag Or Hesitation On Acceleration.
6. Two footed drivers could be in torque limiting mode (Enhanced Brake Pedal Override) on 2012 and newer trucks
7. Drivability concerns can be induced by fueling with vehicles running. Do not fill trucks while running.
8. Additional engine vibration for AFM operation, low idle speeds and general performance can be noticed
because of solid engine mounts.
9. While decelerating, when the transmission performs the 2nd to 1st gear downshift, it will match engine RPM to
the new downshifted speed
This can be perceived as a very brief surge but in reality is only a slight reduction in engine braking during the
shift transition to complete the clutch to clutch shift
This is different than the downshifts performed on the older 4-speed automatics that had a freewheeling clutch
that did not require the engine speed matching. This is an expected characteristic
10. Traction Control may activate on dry or rough roads or under conditions such as heavy acceleration while
turning or abrupt upshifts/downshifts of the transmission.
When this happens, a reduction in acceleration may be noticed, or a noise or vibration may be heard. This is normal.

Warranty Information
For vehicles repaired under warranty use:
Labor Operation

Description

Labor Time

2810075

Engine Control Module Reprogramming with SPS

Use Published Labor
Operation Time

2810215

Body Control Module Reprogramming with SPS

Use Published Labor
Operation Time

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.