Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
2007 Chevrolet TrailBlazer 4WD L6-4.2LFACTORY OEM SERVICE PROCEDURE
Instruments - Erratic Speedometer Operation
Bulletin No.: 07-08-49-027
Date: December 04, 2007
TECHNICAL
Subject:
Erratic Speedometer Operation Or Speedometer Needle Shakes Above 60 mph (96 km/h) (Repair Poor Connection At Ground G108)
Models:
2004-2007 Buick Rainier
2002-2008 Chevrolet TrailBlazer Models
2002-2008 GMC Envoy Models
2002-2004 Oldsmobile Bravada
2005-2008 Saab 9-7X
with 4.2L Engine Only (VIN S - RPO LL8)
Condition
Some customers may comment on erratic operation of the speedometer. Others may comment that the speedometer needle shakes above 96 km/h (60 mph).
Cause
This condition may be caused by a loose or poor connection at Powertrain Control Module/Engine Control Module (PCM/ECM) ground G108.
Correction
Technicians are to inspect and repair ground G108 as necessary. Refer to callout 1 in the illustration above for the location of G108. Refer to the Testing for Intermittent Conditions and Poor Connections and the Wiring Repair procedures in SI for more information.
Warranty Information (excluding Saab U.S. Models)
For vehicles repaired under warranty, use the table.
Warranty Information (Saab U.S. Models)
For vehicles repaired under warranty, use the table.
Disclaimer
Date: December 04, 2007
TECHNICAL
Subject:
Erratic Speedometer Operation Or Speedometer Needle Shakes Above 60 mph (96 km/h) (Repair Poor Connection At Ground G108)
Models:
2004-2007 Buick Rainier
2002-2008 Chevrolet TrailBlazer Models
2002-2008 GMC Envoy Models
2002-2004 Oldsmobile Bravada
2005-2008 Saab 9-7X
with 4.2L Engine Only (VIN S - RPO LL8)
Condition
Some customers may comment on erratic operation of the speedometer. Others may comment that the speedometer needle shakes above 96 km/h (60 mph).
Cause
This condition may be caused by a loose or poor connection at Powertrain Control Module/Engine Control Module (PCM/ECM) ground G108.
Correction
Technicians are to inspect and repair ground G108 as necessary. Refer to callout 1 in the illustration above for the location of G108. Refer to the Testing for Intermittent Conditions and Poor Connections and the Wiring Repair procedures in SI for more information.
Warranty Information (excluding Saab U.S. Models)
For vehicles repaired under warranty, use the table.
Warranty Information (Saab U.S. Models)
For vehicles repaired under warranty, use the table.
Disclaimer
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.