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.
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HOMESERVICE MANUALSISUZU2006ASCENDER S, 5.3 M, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 399 (DATA COMMUNICATION SYSTEM)DIAGNOSTIC INFORMATION & PROCEDURESSCAN TOOL DOES NOT COMMUNICATE WITH HIGH SPEED GMLAN DEVICECIRCUIT/SYSTEM TESTING
2006 Isuzu Ascender S, 5.3 M, 4WD
Circuit/System Testing
2006 Isuzu Ascender S, 5.3 M, 4WDSECTION Circuit/System Testing
WARNING: This page is about a different car, the 2008 Isuzu Ascender, 2008 GMC Envoy, and 2008 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
- Ignition OFF, disconnect the harness connector of the transmission control module (TCM).
- Test for 108-132 ohms between the serial data circuit terminal 6 and terminal 7.
- If less than the specified range, test the serial data circuits for a short between them. If the circuits test normal, replace the 120 ohm resistor.
- If greater than the specified range, test the serial data circuits for open/high resistance. If the circuits test normal, replace the 120 ohm resistor.
- Ignition ON, test for less than 1.0 volt between the serial data circuit terminal 6 and ground, and between terminal 7 and ground.
- If greater than the specified range, test the serial data circuit for a short to voltage.
- Test for infinite resistance between the serial data circuit terminal 6 and ground, and between terminal 7 and ground.
- If less than the specified value, test the serial data circuit for a short to ground.
- Test for 108-132 ohms between the serial data circuit terminal 37 and terminal 38.
- If less than the specified range, test the serial data circuits for a short between them. If the circuits test normal, replace the ECM.
- If greater than the specified range, test the serial data circuits for open/high resistance. If the circuits test normal, replace the ECM.
- Ignition ON, test for less than 1.0 volt between the serial data circuit terminal 37 and ground, and between terminal 38 and ground.
- If greater than the specified range, test the serial data circuit for a short to voltage. If the circuits test normal, replace the ECM.
- Test for infinite resistance between the serial data circuit terminal 37 and ground, and between terminal 38 and ground.
- If less than the specified value, test the serial data circuit for a short to ground. If the circuits test normal, replace the ECM.
- If the circuits test normal, replace the TCM.
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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.