Subaru OBD-II 1996 & Newer models DTC P1594 – Automatic transmission diagnosis input signal circuit malfunction
DTC P1594 meaning on Subaru OBD-II 1996 & Newer models
DTC P1594 indicates a malfunction in the automatic transmission diagnosis input signal circuit on Subaru vehicles compliant with OBD-II standards from 1996 onwards.
Subaru OBD-II 1996 & Newer models DTC P1594 symptoms
- Check Engine Light (CEL) illuminated on the dashboard
- Transmission shifting issues
- Vehicle may go into limp mode
Subaru OBD-II 1996 & Newer models DTC P1594 causes
- Wiring harness issues
- Faulty transmission control module (TCM)
- Defective transmission speed sensor
Subaru OBD-II 1996 & Newer models DTC P1594 seriousness
The seriousness of DTC P1594 lies in the potential transmission operation problems it can cause. Ignoring this issue can lead to further damage to the transmission system and affect the vehicle’s drivability.
How to diagnose DTC P1594 on Subaru OBD-II 1996 & Newer models
- Use an OBD-II scanner to retrieve the trouble codes and freeze frame data
- Inspect the wiring harness for any visible damage or loose connections
- Check the transmission speed sensor for proper operation
- Test the transmission control module (TCM) for functionality
How to fix DTC P1594 on Subaru OBD-II 1996 & Newer models
- Repair or replace any damaged wiring in the transmission diagnosis input signal circuit
- Replace the transmission speed sensor if found faulty
- If the TCM is defective, it may need to be replaced or reprogrammed
- Clear the trouble codes and test drive the vehicle to ensure the issue is resolved
How to erase DTC P1594 on Subaru OBD-II 1996 & Newer models
- Use an OBD-II scanner to clear the trouble codes
- Alternatively, disconnect the vehicle’s battery for a few minutes to reset the system
- After clearing the codes, perform a test drive to confirm the issue has been resolved
Recommended tools for Subaru OBD-II 1996 & Newer models diagnostics
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