DTC 33

Code 33 - Mass Air Flow (MAF) Sensor:

Wiring Diagram for Mass Air Flow (MAF) Sensor:

CODE 33 - MASS AIR FLOW SENSOR (MAF) SIGNAL FREQUENCY HIGH

Circuit Description:

The MAF sensor measures the flow of air entering the engine. The sensor produces a frequency output between 32 and 150 hertz. A large quantity (high frequency) indicates acceleration, and a small quantity (low frequency) indicates deceleration or idle. This information is used by the ECM for fuel control and the frequency is used by the ECM which converts the signal to flow in gram per second per cylinder. A normal reading is about 5-8 grams per second at idle.

Code 33 will set if:

^ Engine is running less than 1300 rpm.

^ TPS is 8% or less (about .5 volt above idle voltage).

^ Air Flow greater than 20 grams per second (high frequency).

^ All of the above are met for 3 seconds. The "Scan" tool is not of much use in diagnosing this code, but may be useful in comparing the signal of a problem vehicle with that of a known good running one.


Test Description: Numbers below refer to circled numbers on the diagnostic chart.

1. Checks to see if the cause of the Code 33 still exists.


2. Inspect wire routing of high voltage wires such as spark plug wires. Such wires routed too closely to MAF wiring harness could possibly cause an intermittent Code 33.