Manifold Absolute Pressure/Barometric Pressure Circuit Low
What it means
The engine computer has seen a manifold absolute pressure (MAP) signal voltage below the lowest acceptable level, a reading that does not happen in a healthy engine. The cause is usually electrical, such as a lost reference voltage or the signal wire shorted to ground.
Symptoms4
- Check engine light on.
- Weak acceleration or hesitation.
- Rough idle or occasional stalling.
- Hard starting.
Possible causes5
- Unplugged sensor connector or corroded pins.
- Open circuit in the reference voltage wire to the sensor.
- Signal wire shorted to ground.
- Failed pressure sensor.
- Another sensor sharing the same reference voltage has a short that pulls it down.
How to diagnose5
- Read all codes; low-voltage codes for other sensors such as P0122 point to a shared reference voltage fault.
- Watch the sensor reading on a scan tool; a value near zero with the key on means an electrical fault.
- Inspect the connector and its pins.
- Measure reference voltage and ground at the connector and compare with the manufacturer specification.
- Unplug the sensors that share the reference voltage one at a time to see if one of them pulls it down.
How to fix6
- Clean and reconnect the connector.
- Repair the open reference voltage wire.
- Repair the short between the signal wire and ground.
- Replace any other sensor found pulling down the reference voltage.
- Replace the pressure sensor if the circuit is good and the signal is still low.
- Clear the codes and confirm the sensor reading is logical before and after starting.
Repair cost
In Saudi riyals; the highlighted part is the expected range for this fault.
The cost is low for a connector or wire repair, and reaches the upper end when the pressure sensor is replaced.
Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026
Frequently asked questions
Can a vacuum leak cause this code?
Rarely. A vacuum leak raises manifold pressure and does not pull the signal this low, so this code usually means an electrical fault.
Why did codes for other sensors appear with it?
Some sensors share one reference voltage from the computer, so a short in one of them pulls down the signals of the others too.
This guide is for information only and does not replace an inspection by a qualified technician. If the fault involves brakes, steering, engine temperature, electrics or refrigerant, do not attempt the repair yourself.
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