P1901

P1901
No bus communication with DICE.

Fault symptoms
No bus communication with DICE.

Condition
The following conditions are applicable:
Trionic:
- Engine has started
- No communication for 10 seconds

Diagnostic help
Some of the following symptoms can perhaps be observed:
- Diagnostic trouble code P1921 or P1902 in the TCM.
- Additional diagnostic trouble codes in the Trionic (P1902, P1923 or 1908).
- A/C not working.
- Radiator fan runs continuously or not at all (coolant may boil).
- Radio does not work.
- Engine fails to start.
- Direction indicators do not work.
- Interior lighting does not work.
- Intermittent wiper operation does not work.

Checking the wiring harness
Jiggle the wiring harness at several points and in different directions to detect intermittent breaks and short circuits in the leads. Observe the multimeter, test lamp or diagnostic tool during test.

Diagnostic procedure

1 Check additional diagnostic trouble codes
- Check whether diagnostic trouble code P1902 has been in the Trionic or TCM.

Has diagnostic trouble code P1902 been generated in the Trionic or TCM?
YES
- Continue fault diagnosis for diagnostic trouble code P1902.
NO
- Go to point 2.

2 Checking communication
- Turn the ignition switch to ON.

- Select: All systems/Bus configuration in the diagnostic tool's main menu.
- The diagnostic tool shows MISSING when there is no communication for one or more systems.

Is MISSING shown for one or more systems?
YES
- See fault diagnosis by symptoms: No contact with one or more bus systems. Bus and Diagnostic Communication
NO
- Go to point 3.

3 Checking additional diagnostic trouble codes in the Trionic
- Check whether diagnostic trouble code P1908 has been generated in the Trionic.

Has diagnostic trouble code P1908 been generated in the Trionic?
YES
- Go to point 4.
NO
- Go to point 10.

4 Checking customer complaints

Any complaints that the main instrument unit's speedometer has stopped working?
YES
- Go to point 5.
NO
- Go to point 8.

5 Checking the MIU control module's current supply (+30 circuit)
- Unplug the connector: Main instrument unit 12 - pin connector: (540)

- Check the pins in the control module connector and in-line connectors for pin slide-out and poor contact.
- Connect test lamp 86 11 857 to pin 7 of MIU K12's female connector and a good grounding point.

- The test lamp should light.

Function OK ?
YES
- Go to point 6.
NO
- Repair or replace the relevant lead.
- Go to point 17.

6 Checking the MIU control module's grounding.
- Connect test lamp 86 11 857 to pins 7 and 2 in MIU K12's female connector.

- The test lamp should light.

Function OK?
YES
- Go to point 7.
NO
- Repair or replace the relevant lead.
- Go to point 17.

7 Checking the MIU control module's current supply (+15 circuit)
- Connect test lamp 86 11 857 to pins 1 and 2 in MIU K12's female connector.

- The test lamp should light.

Function OK ?
YES
- Go to point 17.
NO
- Repair or replace the relevant lead.
- Go to point 17.

8 Checking the bus lead connections to the Trionic control module (Bus+)
- Unplug the connector: Trionic control module: (430)

- Unplug the connector: TCM control module: (502)

- Unplug the connector: Main instrument unit 12-pin connector: (540)

- Check the pins in the control module connector and in-line connectors for pin slide-out and poor contact.
- Plug in the connector. Main instrument unit 12-pin connector: (540)

- Turn the ignition switch to ON.

- Take a voltage reading.
- Red test lead: Trionic control module: 66

- Black test lead: Good grounding point.
- A reading of 1.5 - 3.5 V should be obtained

Function OK ?
YES
- Go to point 9.
NO
- Repair or replace the relevant lead.
- Go to point 17.

9 Checking the bus lead connections to the Trionic control module (Bus-)
- Take a voltage reading.
- Red test lead: Trionic control module: 19

- Black test lead: Good grounding point.
- A reading of 1.5 - 3.5 V should be obtained

Function OK ?
YES
- Go to point 17.
NO
- Repair or replace the relevant lead.
- Go to point 17.

10 Checking the DICE control module's current supply (+30 circuit)
- Unplug the connector: DICE: (628)

- Check the pins in the control module connector and in-line connectors for pin slide-out and poor contact.
- Connect test lamp 86 11 857 to pin 26 of the control module's female connector and a good ground.

- The test lamp should light.

Function OK ?
YES
- Go to point 11.
NO
- Repair or replace the relevant lead.
- Go to point 17.

11 Checking the DICE control module's grounding
- Connect test lamp 86 11 857 to pins 26 and 57 of the control module's female connector.

- The test lamp should light.

Function OK ?
YES
- Go to point 12.
NO
- Repair or replace the relevant lead.
- Go to point 17.

12 Checking the DICE control module's current supply (+15 circuit)
- Connect test lamp 86 11 857 to pins 64 and 57 of the control module's female connector.

- The test lamp should light.

Function OK?
YES
- Go to point 13.
NO
- Repair or replace the relevant lead.
- Go to point 17.

13 Checking bus leads between the DICE and MIU (Bus+)
- Unplug the connector: Main instrument unit 12-pin connector: (540)

- Take a resistance reading
- Red test lead: DICE: 14

- Black test lead: Main instrument unit 12-pin connector: 5
- A reading of 0-1 ohm should be obtained

Function OK?
YES
- Go to point 14.
NO
- Repair or replace the relevant lead.
- Go to point 17.

14 Checking bus leads between the DICE and MIU (Bus-)
- Take a resistance reading
- Red test lead: DICE: 5

- Black test lead: Main instrument unit 12-pin connector: 12
- A reading of 0-1 ohm should be obtained

Function OK ?
YES
- Go to point 15.
NO
- Repair or replace the relevant lead.
- Go to point 17.

15 Checking whether the bus leads are shorted to ground (Bus+)
- Turn the ignition switch to ON.

- Take a voltage reading.
- Red test lead: DICE: 14

- Black test lead: Good grounding point.
- A reading of 1.5-3.5 V should be obtained

Function OK?
YES
- Go to point 16.
NO
- Repair or replace the relevant lead.
- Go to point 17.

16 Checking whether the bus leads are shorted to ground (Bus-)
- Take a voltage reading.
- Red test lead: DICE: 5

- Black test lead: Good grounding point.
- A reading of 1.5-3.5 V should be obtained

Function OK?
YES
- Go to point 17.
NO
- Repair or replace the relevant lead.
- Go to point 17.

17 Final check
- Clear the diagnostic trouble codes in all Systems.

- Carry out a drive cycle:
- Drive the car at varying engine loads and rpm for five minutes.
- Evaluate the drive cycle:
- Check whether the diagnostic trouble code has recurred.

Function OK?
YES
- The steps taken to rectify the fault were correct.
NO
- See "Before changing a control module." Before Changing A Control Module