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Multiple Data Communication Codes

  1. Ensure Data Link Connector (DLC) cover is properly seated to DLC. If it is, go to step 3). If it is not, clear all codes, install DLC cover properly and test drive vehicle for more than 10 miles. Enter self-diagnostics and recheck for trouble codes. See ENTERING SELF-DIAGNOSTICS  under SELF-DIAGNOSTICS.
  2. DLC cover contains a serial data line jumper connection. When DLC cover is in place, this jumper connects DLC terminals "M" and "L" to complete the serial data line communication link between all computer systems.
  3. Ensure DLC cover is properly positioned. Enter self-diagnostics and record all trouble codes. See ENTERING SELF-DIAGNOSTICS  under SELF-DIAGNOSTICS. If both Codes I033 and I037 are set, repair open in Tan wire between DERM and IPC or between ACP and PCM. Diagnostic Energy Reserve Module (DERM) is located directly above brake pedal. DERM has Yellow connector and wiring harness. A/C Programmer (ACP) is located left of PCM, behind glove box. If both Codes I034 and I037 are set, repair open in Tan wire between IPC and PCM or between ACP and DERM. See WIRING DIAGRAMS.
  4. If both Codes I034 and E052 are set, PCM has lost power. Diagnose as per PCM Code P052. See the TESTS W/CODES - Eldorado or TESTS W/CODES - 4.6L - Seville article in the ENGINE PERFORMANCE section. If Codes I032 or I032 and I034 are set, diagnose as per IPC Code I032. If both Codes I034 and E047 are set, IPC has lost communications with PCM. Diagnose as per IPC Code I034. If both Codes I037 and A037 are set, IPC has lost communications with ACP. Diagnose as per IPC Code I037.
  5. If Codes A037, P047 and T072 are set (I052 may also be set), there is serial data line communication link break down. Diagnose as per IPC Code I052. If Codes I039 and T072 are set, there is a loss of Road Sensing Suspension (RSS) data. Diagnose as per IPC Code I039.
  6. If Codes I032, I033, I034 and I037 are all set, and these are current ("C") codes, go to next step. If these are history ("H") codes, check the following and repair as needed:
    • Check for poor connections at IPC terminals C1 and C2. See Figure.
    • Check for intermittent short to ground or short to battery voltage anywhere in Tan wire circuit.
    • Check for intermittent open in Tan wire circuit between IPC and DERM and between IPC and PCM.
    • Check each computer component along Tan wire circuit to be holding serial data line at a constant voltage.
  7. Disconnect PCM connector C2. See Figure. PCM is located on right kick panel. Remove DLC cover. Using DVOM, measure voltage at DLC terminal "M". If voltage does not fluctuate between 3 and 5 volts, go to step 14). If voltage fluctuates between 3 and 5 volts, disconnect ACP connector and reconnect PCM connector C2. ACP is left of PCM. Using DVOM, measure voltage at DLC terminal "M".
  8. If voltage is fluctuating between 3 and 5 volts, go to step 10). If voltage is not fluctuating between 3 and 5 volts, disconnect PCM connectors. Using jumper wire, connect PCM harness connector C2, terminals 2C12 and 2C13. See Figure.
  9. Using DVOM, measure voltage at DLC terminal "M". If voltage is fluctuating between 3 and 5 volts, check PCM MEM-CAL for good connection into PCM, and check PCM connectors for good connections. If no connection problems exist, replace PCM. If voltage is not fluctuating between 3 and 5 volts at terminal "M", repair short in Tan wire circuit between ACP and PCM.
  10. Disconnect Road Sensing Suspension (RSS) module mounted on board in electronics bay on right side of trunk. Reconnect ACP. Using DVOM, measure voltage at DLC terminal "M". If voltage is fluctuating between 3 and 5 volts, go to step 12). If voltage is not fluctuating between 3 and 5 volts, go to next step.
  11. Disconnect ACP. Connect a jumper wire between ACP connector terminals C10 and C11. See Fig 1. Using DVOM, measure voltage at DLC terminal "M". If voltage is fluctuating between 3 and 5 volts, repair short in Tan wire between ACP and RSS module. If voltage is not fluctuating between 3 and 5 volts, ensure proper MEM-CAL insertion in ACP and proper terminal contact at ACP. If no problems are found, replace ACP.
  12. Connect a jumper wire between RSS C2 (Green) connector terminals C15 and D16. See Figure. Using DVOM, measure voltage at DLC terminal "M". If voltage is not fluctuating between 3 and 5 volts, go to next step. If voltage is fluctuating between 3 and 5 volts, check for proper terminal contact at RSS connector. If terminal contact is okay, replace RSS module.
  13. Disconnect Electronic Brake Control Module (EBCM) connector. EBCM is mounted to center of cross brace behind rear seat and is accessible from trunk. Using DVOM, measure voltage at DLC terminal "M". If voltage fluctuates between 3 and 5 volts, replace EBCM. If voltage does not fluctuate between 3 and 5 volts, repair short in Tan wire between ACP and DLC terminal "L".
  14. Ensure PCM connector and DLC cover are still disconnected. Disconnect Yellow DERM connector. DERM is mounted behind instrument panel above brake pedal. Using DVOM, measure voltage at DERM harness connector terminal B11. See Fig 2. If voltage is not fluctuating between 3 and 5 volts, go to step 16). If voltage is fluctuating between 3 and 5 volts, use jumper wire to connect DERM harness connector terminals A11 and B11. Measure voltage at DLC terminal "M".
    Fig 1: Identifying ACP Connector Terminals
    G92E05245Courtesy of GENERAL MOTORS CORP.
    Fig 2: Identifying DERM Connector Terminals
    G92G05246Courtesy of GENERAL MOTORS CORP.
  15. If voltage fluctuates between 3 and 5 volts at DLC terminal "M", check connections at DERM terminals. If connections are good, replace DERM. If voltage does not fluctuate between 3 and 5 volts at DLC terminal "M", repair short in Tan wire circuit between DERM and DLC terminal "M". See WIRING DIAGRAMS.
  16. Turn ignition off. Disconnect IPC connectors. Leave DERM disconnected. Using DVOM, measure resistance to ground from IPC harness connector terminal C1. See Figure. If resistance is 2000 ohms or less, repair short in Tan wire circuit between DERM and IPC. See WIRING DIAGRAMS.
  17. If resistance is greater than 2000 ohms, connect jumper wire from DERM harness connector terminal B11 to ground. Measure resistance to ground from IPC harness connector terminal C1. If resistance is more than 2000 ohms, repair open in Tan wire circuit between IPC and DERM.
  18. If resistance is 2000 ohms or less, ensure PCM is still disconnected. Measure resistance from ground to IPC harness connector terminal C2. If resistance is more than 2000 ohms and terminal connections are good at IPC connectors, replace IPC. See INSTRUMENT PANEL CLUSTER  under REMOVAL & INSTALLATION.
  19. If resistance is now 2000 ohms or less, repair short in Tan wire circuit between IPC and PCM. After all repairs are completed, clear all codes and verify correct operation.
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