What this code means
P1129 may indicate that the ECM/PCM is seeing a MAP sensor signal higher than expected for the current operating condition.
What the vehicle may do
- The vehicle may have a check engine light.
- The engine can have drivability symptoms depending on when the signal problem occurs.
- The concern may be intermittent if the monitor passes during testing.
Possible fault areas
- Possible vacuum leaks or intake-side air leaks.
- Possible MAP sensor signal performance issue.
- Possible poor connections or loose terminals at the MAP sensor or PCM.
Diagnostic path
Open
On this Honda CR-V, P1129 points to a MAP sensor signal that is higher than expected. In plain terms, the computer may be seeing manifold pressure that does not fit the engine’s operating condition. The vehicle may have a check engine light, and depending on the situation it can have drivability symptoms, but this code is mainly handled as a sensor performance and plausibility check. The broad fault areas may include vacuum leaks, MAP sensor signal behavior, and connection issues at the MAP sensor or PCM. Before getting into the code path, start with the basic system checks so you are not chasing a code with a simple system problem still present.
Check for vacuum leaks first
Start with the vacuum leak check. Look over the PCV valve and hose, EVAP canister purge valve, throttle body, intake manifold, brake booster, and brake booster hose. If you find a vacuum leak, repair or replace the leaking part before going any farther. If there are no vacuum leaks, move on to the MAP sensor performance check.
Run the MAP sensor performance check
Next, warm the engine under the specified no-load condition. Start the engine, hold it at 3,000 rpm with the transmission in P or N until the radiator fan comes on, then let it idle. With the HDS, watch the MAP sensor reading for 5 seconds. The key check here is whether the MAP SENSOR value is more than 36.9 kPa, and whether it stays at that threshold for 5 seconds or more. If it does, replace the MAP sensor. If it does not, continue into problem verification.
Verify the problem under the monitor conditions
For problem verification, clear the DTC with the HDS, then drive the vehicle under the monitor conditions. The engine coolant temperature, ECT SENSOR 1, needs to be above 158 °F (70 °C). Engine speed needs to be between 1,400－6,700 rpm, with the transmission in D. Drive at a steady speed between 55－75 mph (90－120 km/h) for 10 seconds, then decelerate with the throttle fully closed for 2 seconds. Treat those as the conditions needed to get the monitor to make a decision, not as a general road test.
Read the OBD status decision
After the drive, monitor the OBD STATUS for P1129 in the HDS. If it shows FAILED, the failure has been duplicated, and the next action is to replace the MAP sensor. If it shows PASSED, treat it as an intermittent failure; the system is OK at this time, so check for poor connections or loose terminals at the MAP sensor and the PCM. If captured operating data is available for this DTC, try to reproduce the failure under those same conditions. If the status shows NOT COMPLETED, pause, recheck the earlier problem-verification path, and avoid guessing.
Close
The takeaway on P1129 is to prove the basics first, then let the MAP signal test and the OBD status decide the next move. Do not condemn the sensor until the procedure points there, and if the monitor will not complete, go back through the verification conditions carefully. For more diagnostic training, visit stepdiagnostics.com.
Final check
This code is often approached by checking for vacuum leaks first, then testing MAP sensor plausibility and confirming the result with the scan tool status.
For more guided automotive diagnostics, visit STEP Diagnostics.
