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Home >> Saab >> 2001 >> 9-5 Base, 4D Sedan, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Fault Code Diagnosis >> P1625: No Bus Data From ECM Or TCM >> Fault Isolation Procedure

Fault Isolation Procedure

  1. Check whether DICE can communicate with a bus-connected control module: Is MISSING flashing for all systems except DICE on the diagnostic tool's display? If so, go to step  5, otherwise go to next step.
  2. Checking that the control modules allow diagnostic communication: See CONTROL MODULE CONNECTIONS  to determine whether a missing control module allows diagnostics communication. If diagnostic communication is allowed, go to step  4, otherwise go to next step.
  3. Diagnostic procedure for the control module's current supply: See CONTROL MODULE CONNECTIONS  for the fuses which must be intact and the pins which must have a current supply (+30 and +15 circuits) and ground connection in order for a missing control module to allow diagnostic communication. go to step  8.
  4. Diagnostic procedure for the bus wiring harness: The cause of the fault is an open circuit on bus+ or bus- (if only the ECM or TCM and ECM are missing, the fault could also be due to a short circuit in the P bus). go to step  8.
  5. Checking the I-bus:
    • Turn the ignition switch to the ON position.
    • Press NIGHT PANEL on the SID.
    • The main instrument unit's odometer display should go out.
    If the function is correct, go to step  7, otherwise go to next step.
  6. Diagnostic procedure for the bus wiring harness: The cause of the fault is a short circuit in the I-bus+ or I-bus- at some point in the connected wiring harness or internally in a connected control module. go to step  8.
  7. Diagnostic procedure for the DICE bus wiring harness: The cause of the fault is an open circuit between pin 14 of the DICE and crimp connection J72 (green lead) or between pin 5 of the DICE and crimp connection J73 (white lead). The diagnostic instrument shows OK when communication starts. go to step  9.
  8. Diagnostic procedure:
    • Turn the ignition switch to the ON position.
    • Select All systems/Bus configuration in the diagnostic tool's main menu.
    • Jiggle the leads and in-line connectors at several places and in different directions to reveal intermittent breaks and short circuits in the wiring harness. Observe the multimeter, test lamp or diagnostic tool while doing this.
    • The diagnostic instrument shows OK when communication starts.
    • If necessary, disconnect one control module at a time to trace a possible fault.
    • The potential between bus+ and ground and between bus- and ground should be 2-3 volts. All control modules put out this voltage.
    • Rectify the fault.
    Go to next step.
  9. Final check:
    • Clear the DTCs in all systems.
    • Carry out a functionality test.
    If the function is correct, the fault has been rectified, otherwise the control module is faulty and must be changed.
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