Powertrain Controls - ECM/PCM

Diagnostic Chart:

Diagnostic Chart (Cont'd):

Circuit Schematic:

Altitude V. Voltage Range Chart:

MAP CIRCUIT - VOLTAGE OUT OF RANGE LOW
The manifold absolute pressure (MAP) sensor is a variable resistor that responds to changes in manifold pressure (vacuum). The PCM measure the voltage drop across the MAP sensor. The voltage ranges from 1-1.5 volts at idle (high vacuum) to 4-4.5 volts at wide-open throttle (low vacuum).

DTC PARAMETERS

DTC 34 will set if either:
^ Engine speed is less than 1200 rpm.
^ MAP is 0.2 volts or less.
^ DTC 21 and 22 are not present.
or
^ Engine speed is greater than 1200 rpm.
^ MAP is 0.2 volts or less.
^ TP sensor is greater than 15.2 present.
^ DTC 21 and 22 are not present.

DIAGNOSTIC AIDS
When attempting to diagnose an intermittent problem use the Scan tool[1] to review supplemental diagnostic information. The supplemental data can be used to duplicate a problem.

Intermittents or opens suspected to be at the connector can be detected by using Diagnostic Service Probe. Voltage can be read on both wires without disconnecting any connectors.

With the engine Off and key On the map reading should be the same as to barometric because manifold pressure is equal to atmospheric pressure (no vacuum - high voltage). Comparing this reading to a known good vehicle with the same sensor is a good way to check accuracy of a suspect sensor. Readings should be within 0.4 volts.

[1] Select Malfunction History from Scan toot Engine Control (EC) menu.