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.
DTC P0988: Low-Reverse Brake Pressure Switch System: Diagnosis
- STEP 1. Check the DTC.
Q: Is the DTC other than the pressure switch set? (Is the code other than P0841, P0846, P0871, P0876, and P0988 set?)
YES: Check and repair the relevant DTC system.
NO: Go to Step 2.
- STEP 2. Check the TCM terminal voltage.
[C-37 TCM connector (vehicle side, connected)]
Measure the voltage between C-37 terminal No. 43 and body ground.
- Low-reverse brake engaged: 0 V
- Other than above: Battery positive voltage
Q: Is the check result normal?
YES: Go to Step 3.
NO: Go to STEP 7.
- STEP 3. Check between the TCM connector and A/T control solenoid valve assembly.
Check for continuity between C-37 TCM connector and B-111 A/T control solenoid valve assembly connector.
- Between C-37 terminal No. 43 and B-111 terminal No. 7: Continuity exists.
When the continuity check result is OK, check that the wiring harness is not shorted to the body and other wiring harness.
Q: Is the check result normal?
YES: Go to Step 4.
NO: Repair or replace the failure section.
- STEP 4. Check the TCM, A/T control solenoid valve assembly connector pin terminals, and the connection status.
Q: Is the check result normal?
YES: Go to Step 5.
NO: Repair or replace the failure section.
- STEP 5. Check between the A/T control solenoid valve assembly connector and low-reverse brake pressure switch.
Check for continuity between the B-111 A/T control solenoid valve assembly connector terminals and the low-reverse brake pressure switch connector terminals.
- Between B-111 terminal No. 7 and low-reverse brake pressure switch: Continuity exists.
When the continuity check result is OK, check that the wiring harness is not shorted to the body and other wiring harness.
Q: Is the check result normal?
YES: Go to Step 6.
NO: Repair or replace the failure section.
- STEP 6. Check the low-reverse brake pressure switch body ground.
Check for continuity between the low-reverse brake pressure switch body and ground.
- Between the low-reverse brake pressure switch body and body ground: Continuity exists.
Q: Is the check result normal?
YES: Replace the valve body assembly, and then go to STEP 8.
NO: Repair or replace the failure section.
- STEP 7. Check the TCM, A/T control solenoid valve assembly connector pin terminals, and the connection status.
Q: Is the check result normal?
YES: Go to STEP 9.
NO: Repair or replace the failure section.
- STEP 8. Erase the DTC code, and drive the vehicle for a while.
Check that the normal code is displayed.
Q: Is the check result normal?
YES: The procedure is complete.
NO: Replace the TCM.
- STEP 9. Erase the DTC code, and drive the vehicle for a while.
Check that the normal code is displayed.
Q: Is the check result normal?
YES: The procedure is complete.
NO: Return to START.
NO RELATED
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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.