Code E034
MASS AIR FLOW (MAF) SENSOR
FREQUENCY LOW
Circuit Description:
The Mass Air Flow (MAF) sensor measures the amount 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 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 and with the aid of MAF sensor tester J-36101 or equivalent. Code E034 will set when either of the following sets of conditions exists:
^ Engine running
^ No MAF sensor signal for 250 m sec. OR
^ Engine running over 1400 rpm
^ TPS over 2.5 volts
^ Air Flow less than 10 grams per second (low frequency)
^ Above conditions for over 10 sec.
Test Description: The following numbered steps correspond with the step numbers on the diagnostic chart.
1. The Diagnostic Display, ED21 (MAF), is of little use in diagnosing this fault, because when the code is set, a default based on TPS is displayed in place of the actual MAF input to the ECM. A loose or damaged air duct may set a Code E034 and must be checked. If the Mass Air Flow Sensor fault is still present, Code E034 should reset
within one minute. If the code does not reset, the fault was intermittent and MAF Sensor test J- 36101 or equivalent should be used to test the sensor.
2. This step verifies that the reference signal from the ECM is present at MAF sensor harness connector terminal "B". Less than 4 or over 6 volts at this point indicates a faulty CKT 492, connection, or ECM. 3. Verifies that both ignition voltage and a good ground circuit are available.
Diagnostic Aids:
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.
Check For:
^ Poor Connection or Damaged Harness: Inspect ECM harness connectors for backed out terminal "B6", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
^ Intermittent Test: If connections and harness checks out ok, monitor ED21 (MAF) display while moving related connectors and wiring harness. If the failure is induced, the "MAF" display will abruptly change. This will help to isolate the location of the malfunction.
^ Miss-routed Harness: Inspect MAF sensor harness to insure that it is not too close to high voltage wires, such as spark plug leads.
^ Miscalibrated MAF Sensor: The Mass Air Flow Sensor may be tested for being out of specification by using a MAF Sensor test tool J-36101 or equivalent.
Diagnostic Aids:
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.
Check For:
^ Poor Connection or Damaged Harness Inspect ECM harness connectors for backed out terminal "A11", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
^ Intermittent Test If connections and harness checks out ok, monitor A Digital Voltmeter connected from ECM terminal "A11" to ground while moving related connectors and wiring harness. If the failure is induced, the voltage reading will abruptly change. This will help to isolate the location of the malfunction.
^ Symptom Indicators
- If Cam Signal from Cam Sensor to C(3)I module is lost while running, engine will not restart after shutdown.
- If Cam Signal output from the module or wiring etc., to the ECM has failed, engine will restart after shutdown.