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Home >> Saab >> 2001 >> 9-5 Base, 4D Sedan, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Fault Code Diagnosis >> P1623: No Bus Data From TCM >> Fault Isolation Procedure

Fault Isolation Procedure

  1. Checking communication:
    • Turn the ignition switch to the ON position.
    • Select: All systems/Bus configuration in the diagnostic tool's 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 tool shows MISSING when there is no communication for one or more systems. If 'MISSING' is displayed for any system or systems, follow the appropriate fault diagnosis procedure and go to step  10. If all systems are responding, go to next step.
  2. Checking DTCs in the TCM: Check whether DTC P1921 is presented in the TCM. If so, go to step 6, otherwise go to next step.
  3. Checking the control module +30 power supply:
    • Unplug the connector: Control module, TCM 502.
    • Check the pins in the control module connector and in-line connectors for displacement and poor contact.
    • Connect Test Lamp (86 1 857) to pin 20 of the control module's female connector and a good grounding point.
    • 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.
    If the test lamp illuminates, go to next step, otherwise repair or replace the lead concerned and go to step  18.
  4. Checking the control module grounding:
    • Connect Test Lamp (86 1 857) to pins 20 and 42 of the control module's female connector.
    • 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.
    If the test lamp illuminates, go to next step, otherwise repair or replace the lead concerned and go to step  18.
  5. Checking The Wiring harness:
    • Connect Test Lamp (86 1 857) to pins 21 and 42 of the control module's female connector.
    • 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.
    If the test lamp illuminates, go to step  18, otherwise repair or replace the lead concerned and go to step  18.
  6. Checking the bus lead connections to the ECM control module (Bus+):
    • Unplug the connector: ECM control module 430.
    • Unplug the connector: Control module, TCM 502.
    • Check the pins in the control module connector and in-line connectors for displacement and poor contact.
    • Take a voltage reading: 66 ECM control module, B-. (430:66, B-)
    • 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.
    If the diagnostic tool shows a value of 1.5-3.5 volts, go to next step, otherwise repair or replace the lead concerned and go to step  18.
  7. Checking the bus lead connections to the ECM control module (Bus-):
    • Take a voltage reading: 19 ECM control module, B-. (430:19, B-)
    • 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.
    If the diagnostic tool shows a value of 1.5-3.5 volts, go to next step, otherwise repair or replace the lead concerned and go to step  18.
  8. Checking the bus lead connections to the TCM control module (Bus+):
    • Take a voltage reading: 1 TCM control module, B-. (502:1, B-)
    • 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.
    If the diagnostic tool shows a value of 1.5-3.5 volts, go to next step, otherwise repair or replace the lead concerned and go to step  18.
  9. Checking the bus lead connections to the TCM control module (Bus-):
    • Take a voltage reading: 22 TCM control module, B-. (502:22, B-)
    • 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.
    If the diagnostic tool shows a value of 1.5-3.5 volts, go to step  18, otherwise repair or replace the lead concerned and go to step  18.
  10. 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 next step, otherwise go to step  14.
  11. 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  13, otherwise go to next step.
  12. 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  17.
  13. 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  18.
  14. Checking that the control module allows diagnostic communication: See CONTROL MODULE CONNECTIONS  to determine whether a missing control module allows diagnostics communication. If all 'MISSING' systems allow diagnostic communication, go to step  16, otherwise go to next step.
  15. 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  17.
  16. 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 next step.
  17. 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 possible faults.
    • 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.
  18. 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 fault is in the control module.
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