Code 34
MASS AIR FLOW (MAF) SENSOR CIRCUIT
(LOW GM/SEC INDICATED)
3.8L "H" SERIES (PORT)
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, in calculating
fuel delivery. A large quantity of air movement indicates
acceleration, while a small quantity indicates decelleration, 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, and with the aid if MAF Sensor tester J-36101, or
equivalent.
Code 34 will set, when either of the following sets of
conditions exists:
- Engine Running.
- No MAF Sensor signal for 250 msec.
OR
- Engine running over 1400 rpm.
- TPS over 2.5 volts.
- Airflow less than 10 grams per second (low frequency).
- Above conditions for over 10 seconds.
Test Description: Step numbers refer to step
numbers on diagnostic chart.
- This step checks for a loose or damaged air duct, which
could set a Code 34 and also checks to see if ECM
recognizes a problem. A light "OFF" at this
point indicates an intermittent fault.
- A voltage reading at sensor harness connector terminal
"B" of less than 4 or over 6 volts indicates a
fault in CKT 492 or poor connection
- Verifies that both ignition voltage and a good ground
circuit are available.
Check For:
- Poor Connection at ECM pin
"B-6". 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 fualt location.
- Miscalibrated MAF Sensor The Mass
Air Flow Sonsor may be tested, for being out of
specifaction, by using a MAF sensor test tool J-36101, or
equivalent.