TM 1-2840-252-23-3
G-18 FAULT CODE F4, MV POTENTIOMETER EXPANDED INSTRUCTIONS
Refer to numbered steps in figure 104.
Step 2.
Check harness connector PL1 (figure 201) at DECU, and P4 at HMA for tight connections.
Step 3.
Disconnect connectors PL1 and P4 to check pins and sockets.
Step 5.
CAUTION: DO NOT USE AN OHMMETER THAT CAN APPLY MORE THAN 5 mA WHEN
MEASURING RESISTANCES, TO AVOID DAMAGING THE FUEL METERING VALVE
POTENTIOMETER.
With PL1 disconnected, check resistance of HMA (fuel metering valve potentiometer) at
harness
PL1 connector sockets Q and y .(results are "a") and y and KK (results are "b"). Limit for "a"
and "b" is 300 - 5800Ω. Check resistance at sockets g and KK (results are "c"). Limit for "c" is
4250 - 5750Ω. Use the following equation to check wiper resistance:
a + b - c 2 = d
Limit for "d" is ≤ 300-. Use the following equation to check if the high or low limit of the
metering
valve potentiometer has been exceeded:
b - d c = e
Limit for "e" is 0.0710 - 0.9573.
Step 6.
CAUTION: DO NOT USE AN OHMMETER THAT CAN APPLY MORE THAN 5 mA WHEN
MEASURING RESISTANCES, TO AVOID DAMAGING THE FUEL METERING VALVE
POTENTIOMETER.
With P4 disconnected, check resistance of HMA (fuel metering valve potentiometer) at HMA J4
connector pins M and N (results are "f") and N and P (results are "g"). Limit for '"" and "g" is
300 - 5800Ω. Check resistance at pins M and P (results are "h"). Limit for "h" is 4250 - 5750Ω.
Use the following equation to check wiper resistance.
f + g - h 2 = i
Limit for "i" is ≤ 30052'. Use the following equation to check if the high or low limit of the
metering valve potentiometer has been exceeded:
g - i h = j
Limit for "j" is 0.0710 - 0.9573.
Step 7.
Before tightening harness connectors PL1 and P4, be sure that keyways in harness connectors
are aligned with keyways in component connectors.
Step 12. Refer to manufacturer's procedure for diagnosing and replacing harness.
Step 17. Refer to manufacturer's procedure for diagnosing and replacing harness.
G-23
