DTC 34

Code 34 Chart:

Code 34 Wiring Diagram:

CIRCUIT DESCRIPTION:

The Mass Air Flow (MAF) Sensor measures the flow of air, which passes through it in a given time. The Electronic Control Module (ECM) uses this information to determine the operating condition of the engine to control fuel delivery. A large quantity of air movement through the MAF sensor indicates acceleration, while a small quantity of air movement indicates deceleration, or idle.

Code 34 will set, when either of the following sets of conditions exist.

^ Engine running.
^ No MAF sensor signal for 250 msec.

OR

^ Engine running over 1400 rpm.
^ TPS over 2.5 volts.
^ Air Flow less than 10 grams per second (low frequency).
^ Above conditions for over 10 seconds.


NOTE: Because of all the possible color code combinations used on electrical wiring diagrams, always refer to ECM CONNECTOR IDENTIFICATION under ELECTRICAL AND ELECTRONIC WIRING DIAGRAMS for correct color code identification of circuit.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. This step checks for a loose or damaged air duct, which could set code 34 and also checks to see if the ECM recognizes a problem.

2. A voltage reading at the MAF sensor harness connector terminal "B" of less than 4 or over 6 volts indicates a fault in CKT 920 or poor connection.

3. Verifies that both ignition voltage and a good ground circuit are available.




DIAGNOSTIC AIDS:

^ An intermittent may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation.

Check For:

^ Poor connection at ECM pin "B-6". Inspect ECM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.

^ Mis-routed harness. Inspect MAF sensor harness to insure that it is not too close to high voltage wires, such as spark plug leads.

^ Damaged harness. Inspect harness for damage. If harness checks OK, "Scan" while moving related connectors and wiring harness. A change in display would indicate the intermittent fault location.