Code 34 - Manifold Absolute Pressure (MAP) Sensor Circuit

(Signal Voltage Low - High Vacuum)

Circuit Description

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.

A scantool displays manifold pressure in volts. Low pressure (high vacuum) reads a low voltage while a high pressure (low vacuum) reads a high voltage.

If the MAP sensor fails the ECM will substitute a fixed MAP value and use the throttle position sensor (TPS) to control fuel delivery.

Problem Description:

Code 34 will set when:

• Signal voltage is too low (kPa less than 13) and ignition is turned "ON".

  OR

• Engine running greater than 1200 rpm and throttle open greater than 25%

Diagnostic Aids:

An intermittent open in CKTs 432 or 416 will result in a Code 34.

Ignition "ON", engine "OFF". Voltages should be within the values in this chart:

Altitude	Voltage range
below 305	3.8 - 5.5V
305 - 610	3.6 - 5.3V
610 - 914	3.5 - 5.1V
814 - 1219	3.3 - 5.0V
1219 - 1524	3.2 - 4.8V
1524 - 1829	3.0 - 4.6V
1829 - 2133	2.9 - 4.5V
2133 - 2438	2.8 - 4.3V
2438 - 2743	2.6 - 4.2V
2743 - 3048	2.5 - 4.0V

"Scan" Diagnostics:

Engine idling. Does scantool display MAP below 0.25 volts?

NO YES