Mass Air Flow MAF
2-39
12) Check MAF sensor ground circuit.
• Same set-up as previous step, but move YELLOW
test lead to sensor GROUND circuit. Do not probe
MAF RETURN pin. Use backprobe adapter.
Good ground circuit:
TEST light OFF.
Go to next step.
Bad ground circuit:
Any TEST light ON.
Repair open in ground circuit wiring, then retest.
13) Check for connector problems.
• Ignition key OFF.
• Disconnect wiring harness from MAF sensor. (Some
vehicles use a metal snap ring to secure wiring
harness to sensor. Remove this snap ring before
disconnecting wiring harness.)
• Check terminals for damage, corrosion, bad wire
crimps or improper seating in connector.
Repair as necessary, then retest. If no trouble found, go
to next step.
14) Check MAF signal wire for short to ground.
• Verify ignition key OFF and MAF sensor wiring
harness disconnected.
• RANGE on LOW.
• FUNCTION on OHMS.
• YELLOW test lead to MAF signal pin on vehicle
harness connector.
• BLACK test lead to good vehicle GROUND.
Good circuit (no short):
TEST light ON in any position.
Go to next step.
Bad circuit (shorted):
TEST light OFF.
Repair short in signal circuit wiring, then retest.
15) Testing is complete.
Verify ignition key OFF. Set RANGE switch to POWER
OFF and remove all test leads.
If steps 10 through 14 are all good (but step 8
showed a problem) then the sensor is bad and
needs to be replaced.
RANGE
HIGH
LOW
POWER OFF
FUNCTION
VOLTS
OHMS
FREQUENCY
Summary of Contents for CP9087
Page 82: ...3 22 Notes...
