What this code means
P1157 may mean the PCM is seeing a high-voltage type fault in the Sensor 1 air fuel sensor circuit.
What the vehicle may do
- The vehicle may turn on the check engine light.
- Fuel control can be affected, depending on when the fault occurs.
- The symptom may be intermittent if the code does not reset during verification.
Possible fault areas
- Possible A/F sensor circuit concern.
- Possible poor connection or loose terminal at the A/F sensor or PCM.
- Possible open in the AFS plus or AFS minus wiring.
- Possible A/F sensor concern after circuit checks pass.
- Possible PCM software or PCM-related concern after the sensor substitution check.
Diagnostic path
Code meaning and diagnostic frame
On this 2010 to 2016 Honda CR-V with the 2.4 gas engine, P1157 is for the A/F sensor, Sensor 1, AFS circuit high voltage. In plain language, the PCM may be seeing a high-voltage type fault in the Sensor 1 air fuel sensor circuit. The driver may only notice a check engine light, but fuel control can also be affected depending on when the fault occurs. Broadly, this can involve the A/F sensor circuit, poor terminal contact at the sensor or PCM, an open in the AFS plus or AFS minus wiring, the sensor itself after the circuit checks pass, or PCM software and PCM-related concerns after the sensor check is handled.
Verify the problem first
Start by verifying that P1157 is actually active. Turn the vehicle to the ON mode, clear the DTC with the HDS, then start the engine and wait for 1 minute. After that, check for Pending or Confirmed DTCs with the HDS. If P1157 comes back, the failure is duplicated and you move into the circuit checks. If P1157 does not come back, treat it as an intermittent for now. The system is OK at this time, so check for poor connections or loose terminals at the A/F sensor, Sensor 1, and at the PCM. If captured data is available for this code, try to reproduce the captured conditions instead of guessing.
Check the AFS plus wire for an open
With the failure duplicated, turn the vehicle to the OFF (LOCK) mode. Jump the SCS line with the HDS and wait more than 1 minute. Then disconnect the A/F sensor, Sensor 1, 4P connector and PCM connector C, 51P. Now check continuity between the A/F sensor, Sensor 1, 4P connector No. 2 and PCM connector C, 51P, No. 48. If there is continuity, the AFS plus wire is OK and you continue to the AFS minus check. If there is no continuity, repair the open in the AFS plus wire between PCM C48 and the A/F sensor, Sensor 1.
Check the AFS minus wire for an open
Next, keep the same test condition: vehicle OFF (LOCK) mode, A/F sensor, Sensor 1, 4P connector disconnected, and PCM connector C, 51P, disconnected. Check continuity between the A/F sensor, Sensor 1, 4P connector No. 1 and PCM connector C, 51P, No. 47. If there is continuity, the AFS minus wire is OK and the diagnostic moves to the sensor substitution check. If there is no continuity, repair the open in the AFS minus wire between PCM C47 and the A/F sensor, Sensor 1.
Use a known-good sensor to separate sensor from PCM-side faults
After both AFS wires pass continuity, substitute a known-good A/F sensor, Sensor 1. Reconnect all connectors, turn the vehicle to the ON mode, reset the PCM with the HDS, do the PCM idle learn procedure, and check again for Pending or Confirmed DTCs with the HDS. If P1157 is not indicated with the known-good sensor, replace the original A/F sensor, Sensor 1. If P1157 is still indicated, the failure is still duplicated. At that point, update the PCM if it does not have the latest software, or substitute a known-good PCM and recheck. If P1157 goes away after the PCM update, troubleshooting is complete. If P1157 goes away with the known-good PCM substituted, replace the original PCM.
Verification and takeaway
Keep verification separate from the wiring and substitution work. Once the repair path is completed, use the Pending or Confirmed DTC check with the HDS to confirm P1157 stays gone. The key on P1157 is not to condemn the sensor first. Duplicate the fault, prove the AFS plus and AFS minus circuits, then use the known-good sensor and PCM-side checks to make the final call. For more diagnostic training, visit stepdiagnostics.com.
Final check
P1157 is often best approached by duplicating the code first, checking the two sensor signal wires for opens, and only then using known-good component substitution to separate a sensor fault from a PC
For more guided automotive diagnostics, visit STEP Diagnostics.
