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 MANUALSJEEP2009LIBERTY LIMITED, 4WD, PART TIMEREPAIR AND DIAGNOSISTRANSMISSIONTRANSMISSION CONTROL SYSTEMS(TRANSMISSION CONTROL MODULE (TCM) - ELECTRICAL DIAGNOSTICS)DTC TROUBLESHOOTINGU0401-IMPLAUSIBLE DATA RECEIVED FROM ECM/PCMDIAGNOSTIC TEST
2009 Jeep Liberty Limited, 4WD, Part Time
Diagnostic Test
2009 Jeep Liberty Limited, 4WD, Part TimeSECTION Diagnostic Test
- CHECK IF TIPM CAN BUS DTCS ARE PRESENT
- With the scan tool, read TIPM DTCs.
Are there any TIPM CAN BUS DTCs present?
Yes
- Refer to DTC-Based Diagnostics/MODULE, Totally Integrated Power (TIPM) - Diagnosis and Testing for diagnostic procedures and other possible causes.
- Perform NAG1 TRANSMISSION VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Transmission Control (TCM) - Standard Procedure .
No
- Go to step 2
- With the scan tool, read TIPM DTCs.
- CHECK IF ENGINE DTCS ARE PRESENT
- With the scan tool, read Engine DTCs.
Are there any Engine DTCs present?
Yes
- Refer to DTC Based Diagnostics and perform the appropriate diagnostic procedure.
- Perform NAG1 TRANSMISSION VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Transmission Control (TCM) - Standard Procedure .
No
- Using the schematics as a guide, check the Transmission Control Module (TCM) terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace the TCM in accordance with the Service Information.
- Perform NAG1 TRANSMISSION VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Transmission Control (TCM) - Standard Procedure .
- With the scan tool, read Engine DTCs.
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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.