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 ECM uses this information to monitor the operating condition of the engine for fuel delivery calculations. A large quantity of air movement indicates acceleration, while a small quantity indicates deceleration or idle. The MAF sensor produces a frequency signal which cannot be easily measured. The sensor can be diagnosed using the procedures on this chart.

Code 34 will set when of the following conditions exists:

^ Engine running.
^ No MAF sensor signal for 1.5 mS.
^ Above conditions for over 4 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 to see if ECM recognizes a problem.

2. A voltage reading at sensor harness connector terminal "A" of less than 4 or over 6 volts indicates a fault in CKT 492 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, mis-routed harness, rubbed through wire insulation, or a wire broken inside the insulation.

Check for:

^ Poor connection at ECM pin "YD10". Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

^ 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 appears OK, "Scan" while moving related connectors and wiring harness. A change in display would indicate the intermittent fault location.

^ Plugged Air Intake Filter - A WOT acceleration from a stop should cause the MAF reading on the "Scan tool to range from about 4.7 at idle to 100 or greater at the time of the 1-2 shift. If not, check for restriction.