Code 34: Map Sensor Signal Volt Low: Notes

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 closed throttle idle, to 4-4.5 volts at wide open throttle. If the MAP sensor fails, the ECM will substitute a fixed MAP value and use the throttle position sensor (TPS) to control fuel delivery.

1. This test determines if Code 34 is the result of a hard failure or an intermittent condition. A Code 34 will set when the following conditions occur:
   • MAP signal voltage is too low.
   • The engine speed is over 1200 RPM.
2. By jumping harness terminals "B" to "C", and with 5 volts to signal, this will determine if the sensor is at fault, or if there is a problem with the ECM or wiring.
3. The "SCAN" tester may not display 12 volts. The important thing is that the ECM recognizes the voltage as more than 4 volts, indicating that the ECM and circuit No. 432 is okay.