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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 >> P1622: No Bus Data From MIU >> 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 see the fault diagnosis for the appropriate system, when finished, go to step  8. If no systems are showing as 'MISSING' go to next step.
  2. Checking customer complaints: Any complaints that the main instrument unit's speedometer has stopped working? If so, go to step  5, otherwise go to next step.
  3. Checking the bus lead connections to the ECM control module (Bus+):
    • Unplug the connector: ECM control module 430.
    • Unplug the connector: Main instrument unit 12-pin connector 540.
    • Check the pins in the control module connector and in-line connectors for displacement and poor contact.
    • Plug in the connector: Main instrument unit 12-pin connector 540.
    • Unplug the connector: Control module, TCM 502.
    • Take a voltage reading: 66 Control module, ECM and B-. (430:66 and 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 1.5-3.5 volts, go to next step, otherwise go to step  13.
  4. Checking the bus lead connections to the ECM control module (Bus-):
    • Take a voltage reading: 19 Control module, ECM and B-. (430.19 and 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 1.5-3.5 volts, go to step  13, otherwise repair or replace the lead concerned and go to step  13.
  5. Checking the power supply:
    • Unplug the connector: Main instrument unit 12-pin connector 540.
    • 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 7 of the MIU's (K12) 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 step 6, otherwise repair or replace the lead concerned and go to step  13.
  6. Checking the ground lead:
    • Connect Test Lamp (86 1 857) to pins 7 and 2 of the MIU's (K12) 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  13.
  7. Checking the control module's power supply (+15 circuit):
    • Connect Test Lamp (86 1 857) to pins 1 and 2 of the MIU's (K12 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  13, otherwise repair or replace the lead concerned and go to step  13.
  8. 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.
  9. 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  11, otherwise go to next step.
  10. 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 possibly faulty one.
    • The potential between bus+ and ground and between bus- and ground should be 2-3 volts. All control modules put out this voltage.
    When finished, go to step  13.
  11. 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. When finished, go to step 13.
  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  10.
  13. Final check:
    • Repair or replace any faulty leads.
    • 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 replaced.
  14. See CONTROL MODULE CONNECTIONS  to determine whether a missing control module allows diagnostic communication. If all 'MISSING' systems allow diagnostic communication, go to step  12, otherwise check the table again for fuses that 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 diagnostics communication. When finished, go to step  10.
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