Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSSAAB20039-3 CONVERTIBLE (9400) L4-2.0L TURBO (2.0 HOT)REPAIR AND DIAGNOSISA L L DIAGNOSTIC TROUBLE CODES ( DTC )TESTING AND INSPECTIONP CODE CHARTSP1921TCM - (TRANSMISSION CONTROL MODULE)
2003 Saab 9-3 Convertible (9400) L4-2.0L Turbo (2.0 HOT)
TCM - (Transmission Control Module)
2003 Saab 9-3 Convertible (9400) L4-2.0L Turbo (2.0 HOT)SECTION TCM - (Transmission Control Module)
P1921
No Bus data From TRIONIC. See Fault Tracing 3:5 Bus and Diagnostic Communication.
Fault symptoms
CHECK GEARBOX warning lamp on.
TCM in limp-home mode.
Conditions
The diagnostic trouble code is generated when bus communication ceases between Trionic and the TCM (when the engine speed is over 200 rpm and there has been no communication for at least 6 seconds).
Diagnostic help
The TCM goes into limp-home mode.
If Trionic is not connected to the bus, it will not be possible to start the car.
See P1921 Electrical system. (Bus and Diagnostics Communication)
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.