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.
Chart C2, Map Sensor Check
A Manifold Absolute Pressure (MAP) sensor is used to monitor vacuum in the EGR vacuum circuit. It also sends the ECM a barometric pressure (altitude) signal when the ignition switch is on without the engine running or with the engine running when EGR is not in operation. This signal allows the ECM to control altitude related injection pump timing and metering valve travel at wide open throttle. The barometric signal is also used by the ECM along with absolute EGR control pressure, coolant temperature, metering valve position, TCC state, vehicle MPH, and engine RPM to determine and control EGR Pulse Width Modulated (PWM) duty cycle.
- Checks for reference voltage at MAP sensor harness. Normal voltage at terminal "C" of MAP harness should be about 5 volts.
- Checks for an open ground in the MAP circuit to ECM. Normal voltage is about 5 volts with a good ground.
- Checks for proper circuit from the MAP signal wire to ECM terminal "P". Incorrect voltage is an open or grounded wire, or faulty MAP sensor. Normal voltage is shown on table at bottom of chart.
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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.