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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 MANUALSCHEVROLET2002AVALANCHE 2500, RWDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 18 (BODY CONTROL MODULES)SYSTEM TESTSTEST B: SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICETESTING
2002 Chevrolet Avalanche 2500, RWD
Test B: Scan Tool Does Not Communicate With Class 2 Device: Testing
2002 Chevrolet Avalanche 2500, RWDSECTION Testing
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2002 GMC Savana, 2002 Chevrolet Chevy Express, 2001 GMC Savana Special, 2001 GMC Savana Camper Special, and 2001 GMC Savana. However, it is still accessible from the selected car via links, so may be relevant.
- Turn ignition switch to OFF position. Connect scan tool to Data Link Connector (DLC), located below steering column. Turn ignition switch to RUN position. If scan tool powers up, go to next step. If scan tool does not power up, go to TEST A: SCAN TOOL DOES NOT POWER UP .
- Turn ignition switch to RUN position. Attempt to communicate with each module on class 2 serial data line. If scan tool communicates with any module, go to next step. If scan tool does not communicate with any module, go to step 7 .
- Select Display DTCs function for each module. Record all DTCs, DTC status and which module set the DTC(s). If any DTCs between DTC U1000 and U1255 are set, go to next step. If no DTCs between DTC U1000 and U1255 are set, go to DIAGNOSTIC AIDS .
- If DTCs U1300, U1301, or U1305 are retrieved from any module, go to next step. If no DTCs are retrieved, go to step 6 .
- Test the class 2 serial data circuit for a short to ground or short to voltage. If condition is found, repair as necessary and go to step 23 . If no condition is found, go to next step.
- If only DTC U1000 or U1255 are set, go to DTC U1000 OR U1255: CLASS 2 COMMUNICATION MALFUNCTION under DIAGNOSTIC TESTS. If other DTC(s) between DTC U1000 and U1255 are set, go to DTC U1001-U1254: LOSS OF XXX COMMUNICATION under DIAGNOSTIC TESTS.
- Turn ignition switch to OFF position. Disconnect scan tool from DLC. Check DLC terminals No. 2 and 5 for intermittent or poor terminal contact. See Figure . If terminal contact is okay, go to next step. If terminal contact is not okay, repair as necessary. Perform appropriate diagnostic system check. See DIAGNOSTIC SYSTEM CHECK .
- Check for open in Black wire (ground circuit) between ground and DLC terminal No. 4. If Black wire is okay, go to next step. If Black wire is not okay, repair circuit as necessary. Perform appropriate diagnostic system check. See DIAGNOSTIC SYSTEM CHECK .
- Disconnect splice S207, located in instrument panel harness, approximately 2 inches from park brake warning switch breakout, toward data link connector (DLC) breakout, and splice S153, located in engine harness approximately 3 inches from C100 breakout toward PCM breakout (except 6.5L), or in engine harness, approximately 10 inches from A/C compressor clutch breakout toward C100 breakout (6.5L). See Figure . Check for continuity of Purple wire between suspect module and S207 and between S207 and S153. If circuit(s) are okay, go to next step. If circuit(s) are not okay, repair as necessary. After repair, perform appropriate diagnostic system check. See DIAGNOSTIC SYSTEM CHECK table under SELF-DIAGNOSTICS.
- Check for open or short in Purple wire (class 2 serial data circuit) between DLC terminal No. 2 and splice connector S207 terminal "A". See Figure . If Purple wire is okay, go to next step. If Purple wire is not okay, repair circuit as necessary. Perform appropriate diagnostic system check. See DIAGNOSTIC SYSTEM CHECK table under SELF-DIAGNOSTICS.
- Connect a jumper wire between DLC terminal No. 2 (Purple wire) and radio (IRC) harness connector terminal A2 (Purple wire). See Figure and Fig 1 . Turn ignition switch to RUN position. Attempt to communicate with IRC. If scan tool does not communicate with IRC, go to next step. If scan tool communicates with IRC, go to step 13 .
- Turn ignition switch to OFF position. Disconnect IRC Light Gray 24-pin harness connector. Check for short to ground or voltage in Purple wire (class 2 serial data circuit) between DLC terminal No. 2 and IRC harness connector terminal A2. Turn ignition switch to RUN position when checking for short to voltage. See Figure and Fig 1 . If Purple is okay, go to step 21 . If Purple wire is not okay, repair as necessary. After repair, go to step 23 .
- Remove jumper wire from IRC connector, leaving other end connected to DLC terminal No. 2. Connect other end to PCM harness connector as specified. See POWERTRAIN CONTROL MODULE SERIAL DATA CIRCUIT IDENTIFICATION
table. See Figure
, Fig 2
and Fig 3
. Turn ignition switch to RUN position. Attempt to communicate with PCM. If scan tool does not communicate with PCM, go to next step. If scan tool communicates with PCM, go to step 15
.POWERTRAIN CONTROL MODULE SERIAL DATA CIRCUIT IDENTIFICATION
Vehicle Option (RPO Code) Connector/Terminal 8.1L MFI/4.3L CPI HO (L18/L35) C1/58 5.0L CPI/5.7L CPI (L30/L31) C1/59 6.5L Turbo Diesel HO (L65) C3/C8
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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.