Manifold Absolute Pressure/Barometric Pressure Sensor Circuit Intermittent/Erratic

What it means

The manifold absolute pressure (MAP) sensor signal is cutting in and out or jumping around. The manifold absolute pressure (MAP) sensor measures vacuum (pressure) inside the intake manifold so the ECU can calculate engine load and fuel delivery. Intermittent faults are almost always a loose connection, a chafed wire or a sensor that is starting to fail.

Symptoms

• Check engine light on
• Rough idle
• Hesitation and poor power
• Poor fuel economy
• Black smoke from the exhaust
• Hard starting

Probable causes

Most likely first

1. 1Loose or corroded connector terminals
2. 2Wiring chafed and shorting intermittently, often where the harness moves with the engine
3. 3Failing sensor

How to diagnose it

Work through these in order before buying parts

1. 1Record the code and its freeze frame data (speed, load, temperature when it set), then clear it and see if it comes back.
2. 2Inspect the manifold absolute pressure (MAP) sensor connector and wiring (on the intake manifold or connected to it by a vacuum hose). Look for corrosion, bent or pushed-back pins, oil contamination and chafed insulation.
3. 3Watch the manifold absolute pressure (MAP) sensor reading on live data. With key on and engine off it should read close to barometric pressure (about 100 kPa at sea level). At warm idle a healthy engine usually reads 25–40 kPa (high vacuum).
4. 4With the key on and the sensor unplugged, check for about 5 volts on the reference wire and a good ground (under 0.1 V drop) on the ground wire. Back-probe the signal wire with the sensor connected and watch the voltage change smoothly.
5. 5Wiggle the harness and connector while watching live data. A jump in the reading pinpoints the bad spot.
6. 6Check for technical service bulletins (TSBs) or software updates for your make and model; some codes have known factory fixes.

Common fixes

• Repair the damaged wiring or connector
• Replace the manifold absolute pressure (MAP) sensor
• Clear the code and test drive to confirm the repair