The Manifold Absolute Pressure sensor (MAP) responds to changes in manifold pressure (vacuum). The ECM receives this information as a signal voltage that will vary from about 1-1.5 volts at idle to 4-4.5 volts at wide open throttle. If MAP sensor fails the ECM will substitute a fixed MAP value and use the TPS to control fuel delivery.

Code 34 sets when engine speed is less than 1200 RPM, TPS is greater than 20 percent and MAP signal voltage is low. A Code 34 will also result if circuits No. 416 and 432 are open or shorted to ground.

NOTE: Test numbers refer to test numbers on diagnostic chart.

This test confirms Code 34, and determines if code is the result of a hard failure or an intermittent condition.
Jumpering harness terminal "B" to "C" will determine if sensor is at fault or if there is a problem with the ECM or wiring.
"Scan" tester may not display 12 volts. The important thing is the ECM recognizes and sets Code 33, high MAP voltage signal, indicating the ECM and circuit No. 432 are not at fault.

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.

Safety Warning

Code 34 - Map Sensor Signal Volt Low: Notes

Use the Manual With the Right Hardware

When to See a Mechanic

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