P2A0B: Manifold Absolute Pressure Sensor B Circuit Range/Performance

What it means

The MAP B signal does not correlate with TPS, MAF, or RPM as expected. Vacuum leak, restricted port, or sensor drift.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

MAP B measures intake manifold pressure for a secondary load estimate. This code sets when its signal is electrically plausible but does not track expected changes in throttle position, airflow, or engine speed, which can happen with sensor drift, a restricted pressure port, or an intake leak.

Common causes

Most likely first.

1. Vacuum leak in intake
2. Sensor zero drifted
3. Sensor element aged beyond calibration window

Symptoms

• Check-engine light
• Rough idle
• Poor acceleration

How to diagnose it

1. Record freeze-frame data and graph MAP B alongside throttle position, MAF if fitted, RPM, and the primary MAP reading to identify where the signals stop agreeing.
2. Inspect the intake for split hoses, loose joints, and other vacuum leaks that could alter manifold pressure.
3. Check the MAP B pressure port for blockage and inspect its connector and wiring for damage or poor contact.
4. Compare MAP B readings at key-on, idle, and changing engine load with the manufacturer's specification and the primary MAP signal.
5. If the port and intake are sound, test MAP B for drift across operating conditions and replace it only if its readings remain out of range.

Common fixes

• Repair a leaking intake hose, gasket, or connection.
• Clear a restricted MAP B pressure port.
• Repair poor connector contact or damaged MAP B wiring.
• Replace MAP B if it has drifted beyond the manufacturer's specification.

Can I keep driving?

A short drive may be possible if the engine remains stable, but avoid hard acceleration because incorrect load readings can cause hesitation and poor response. Stop if it runs roughly enough to affect control in traffic.