P1921
Read the instructions below then
start the fault diagnostic procedure.
Symptom: No bus communication with Trionic
No Bus data From TRIONIC.
Fault symptoms
No bus communication with Trionic
Condition
The following conditions are applicable:
TCM:
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The automatic transmission input shaft speed exceeded 200 rpm once during the present driving cycle
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No communication for 4 seconds.
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Diagnostic help
Some of the following symptoms
may
be observed:
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Diagnostic trouble codes P1623, P1622, P1901 or P1902 in Trionic (if Trionic can be contacted)
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Additional diagnostic trouble code in the TCM (P1902).
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Automatic transmission in Limp-Home mode (CHECK GEARBOX lamp on).
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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 the test.
