DTC 34

Code 34 Chart:

Code 34 Wiring Diagram:

CIRCUIT DESCRIPTION:

The Mass Air Flow (MAF) Sensor measures the flow of air entering the engine. The sensor produces a frequency output between 32 and 150 hertz (3 gm/sec to 150 gm/sec.). A large quantity (high frequency) indicates acceleration, and a small quantity (low frequency) indicates deceleration or idle. This information is used by the Electronic Control Module (ECM) for fuel control and is converted by a "Scan" tool to read out the air flow in grams per second. A normal reading is about 4-7 grams per second at idle and increase with rpm. The MAF sensor is powered by the MAF sensor relay and the sensor should have power supplied to it anytime the ignition is "ON".

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. Code 34 will set if:

^ Engine running
^ MAF sensor disconnected, faulty relay, or MAF signal circuit shorted to ground OR Air Flow less than 2 grams per second (low frequency)
^ A loose or damaged air duct can set Code 34.
^ This test checks to see if ECM recognizes a problem. A light "OFF" at this point indicates an intermittent problem.

2. Checks to see if 5 volt reference signal from ECM is at MAF sensor harness connector.

3. Checks for l2 volt supply to MAF sensor.

4. Checks for open in l2 volt supply to relay.



DIAGNOSTIC AIDS:

The "Scan" tool is not of much use in diagnosing this code because when the code sets gm/sec will be displaying the default value. However, the "Scan" may be useful in comparing the signal of a problem vehicle with that of a known good running one. Check for loose or damaged air duct. Inspect sensor and relay connections as an open will result in a Code 34. Refer toTESTING PROCEDURES/DIAGNOSIS BY SYMPTOM/INTERMITTENTS.