DTC 34

Code 34 Diagnostic Chart:

Mass Air Flow Sensor Circuit Diagram:

CIRCUIT DESCRIPTION:
The mass air flow (MAF) sensor measures the flow of air which passes through it in a given time. The PCM 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 over 4 seconds.

TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart.
1. This step checks to see if PCM 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 PCM pin "BD14". 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.