Diagnostic Test

2013 Jeep Wrangler Sport, Automatic TransSECTION Diagnostic Test
WARNING: This page is about a different car, the 2016 Jeep Wrangler and 2015 Jeep Wrangler. However, it is still accessible from the selected car via links, so may be relevant.
  1. CHECK FOR DTCS U0001-CAN C BUS DTC or U0121-LOST COMMUNICATION WITH ANTI-LOCK BRAKE MODULE 
    1. With the scan tool, check DTCs.

      Is DTC U0001-CAN C BUS DTC or U0121-LOST COMMUNICATION WITH ANTI-LOCK BRAKE MODULE set?

      Yes 

      • Perform the diagnostic procedure for U0001-CAN C BUS DTC first if it is present.
      • Perform the NAG1 TRANSMISSION VERIFICATION TEST. Refer to STANDARD PROCEDURE .

      No 

      • Go To  2
  2. CHECK FOR ABS DTCS 
    1. With the scan tool, read ABS DTCs.

      Are there any ABS DTCs present?

      Yes 

      No 

      • Using the schematics as a guide, check the Transmission Control Module (TCM) pins, terminals, and connectors for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace and program the TCM in accordance with the Service Information. Refer to MODULE, TRANSMISSION CONTROL .
      • Perform the NAG1 TRANSMISSION VERIFICATION TEST. Refer to STANDARD PROCEDURE .
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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.