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Engine Controls Diagnostic System Check

NOTE: Check for applicable technical service bulletins before proceeding. Do not perform the following procedure if no driveability conditions exists, unless directed here from another procedure. Do not turn ignition off during the following procedure or clear DTCs unless instructed to do so.
  1. If a condition exists with starting system, perform engine electrical diagnostic system check. See ENGINE ELECTRICAL DIAGNOSTIC SYSTEM CHECK . Ensure battery is fully charged and cables are clean and tight. Ensure Powertrain Control Module (PCM) grounds are clean, tight, and in proper location. PCM is located in engine compartment, inside air filter housing. See Fig 1. Install scan tool. If scan tool powers up, go to next step. If scan tool does not power up, see TEST A: SCAN TOOL DOES NOT POWER UP  under SYSTEM TESTS.
  2. Turn ignition on. Try to establish communication with PCM, Electronic Brake Control Module (EBCM) and Vehicle Theft Deterrent (VTD) module. If scan tool communicates with all control modules, go to next step. If scan tool does not communicate with all control modules, diagnose communication problem. See TEST B: SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE  under SYSTEM TESTS.
  3. Try to start engine. If engine starts and idles, go to next step. If engine does not start and idle, diagnose engine cranks, but does not start. See NO START DIAGNOSIS under BASIC DIAGNOSTIC PROCEDURES - CARS - EXCEPT METRO & PRIZM in ENGINE PERFORMANCE.
  4. Using scan tool, select DTC display function for PCM, EBCM and VTD. If any DTCs are present, record DTCs, which module set the DTC and failure record for DTC. Go to next step. If no DTCs are present, go to step  8.
  5. If scan tool does not display any DTCs that begin with "U", go to next step. If scan tool displays any DTCs that begin with "U", diagnose communication problem. See TEST B: SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE  under SYSTEM TESTS.
  6. If scan tool displays DTC P0601, P0602, P0603, P0604, P0606 or P1621, repair DTCs as necessary. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.6L DEVILLE, ELDORADO & SEVILLE article in ENGINE PERFORMANCE. If scan tool does not display any of the codes listed, go to next step.
  7. If scan tool displays DTC P0560, P0562, P0563, P0621 or P0622, see GENERATORS & REGULATORS - DEVILLE article in STARTING & CHARGING SYSTEMS. If scan tool does not display DTC P0562, P0563, P0621 or P0622, go to next step.
  8. If customer's concern is not with the automatic transmission, go to next step. If customer's concern is with the automatic transmission, see HYDRA-MATIC 4T80-E DIAGNOSIS article in AUTOMATIC TRANSMISSIONS for further diagnosis.
  9. If customer's concern is MIL inoperative, diagnose MIL circuits. See MALFUNCTION INDICATOR LIGHT INOPERATIVE under SYSTEM TESTS in SELF-DIAGNOSTICS - 4.6L DEVILLE, ELDORADO & SEVILLE article in ENGINE PERFORMANCE. If customer's concern is MIL always on, diagnose MIL circuits. See MALFUNCTION INDICATOR LIGHT ALWAYS ON under SYSTEM TESTS in SELF-DIAGNOSTICS - 4.6L DEVILLE, ELDORADO & SEVILLE article in ENGINE PERFORMANCE. If customer's concern is a driveability problem, diagnose by symptom. See appropriate TROUBLE SHOOTING - NO CODES - CARS article.
Fig 1: Locating Powertrain Control Module/Air Filter Housing
G00074355Courtesy of GENERAL MOTORS CORP.
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