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.
Circuit Description: Notes
The DTC P1129 Manifold Absolute Pressure (MAP) Sensor High Pressure diagnostic monitors the accuracy of the MAP sensor output. The pressure changes occur based on engine load and the throttle valve opening. The MAP sensor has the following circuits:
- A 5-volt reference circuit
- A low reference circuit
- A signal circuit
The powertrain control module (PCM) supplies 5 volts to the MAP sensor on the 5-volt reference circuit. The PCM also provides a ground on the low reference circuit. The PCM receives a low voltage on the signal circuit when manifold vacuum is high at idle or deceleration. The PCM receives a high voltage when manifold vacuum is low at wide open throttle (WOT) or when the ignition is ON and the engine is OFF. If the MAP sensor output is more than the expected value, a DTC P1129 can set.
The following table illustrates the difference between MAP kPa, signal voltage and engine vacuum.
| Engine Condition | MAP kPa | MAP Signal Voltage | Manifold Vacuum |
|---|---|---|---|
| Idle | Low | Low | High |
| Deceleration | Low | Low | High |
| Ignition ON, Engine OFF | High | High | Zero |
| Wide-Open Throttle | High | High | Low |
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.