TM 1-2840-252-23-3
G-52
FAULT CODE B7, PLA POTENTIOMETER EXPANDED INSTRUCTIONS
Refer to numbered steps in figure 138.
Step 4.
Check harness connector PL3 (figure 201) at DECU, and P4 at HMA for tight connections.
Step 5.
Disconnect connectors PL3 and P4 to check pins and sockets.
Step 7.
CAUTION: DO NOT USE AN OHMMETER THAT CAN APPLY MORE THAN 5 mA WHEN
MEASURING RESISTANCES, TO AVOID DAMAGING THE PLA POTENTIOMETER
With PL3 disconnected, check resistance of HMA (PLA potentiometer) at harness PL3 connector
sockets U and T (results are "a") and T and S (results are "b"). Limitfor "a" and "b" is 510-5750Ω.
Check resistance at sockets U and S (results are "c"). Limit for "c" is4250-5750Ω. Use the
following equation to check wiper resistance:
a + b - c 2 = d
Limit for "d" is < 300Ω. Use the following equation to check if the high or low limit of the PLA
potentiometer has been exceeded:
b - d c = e
Limit for "e" is 0.120 - 0.950.
Step 8.
CAUTION: DO NOT USE AN OHMMETER THAT CAN APPLY MORE THAN 5 mA WHEN
MEASURING RESISTANCES, TO AVOID DAMAGING THE PLA POTENTIOMETER.
With P4 disconnected, check resistance of HMA (PLA potentiometer) at HMA J4 connector pins X
and Y (results are "f") and Y and Z (results are "g"). Limit for "f" and "g" is 510 - 5750Ω. Check
resistance at pins X and Z (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 < 300Ω. Use the following equation to check if the high or low limit of the PLA
potentiometer has been exceed d:
e
g - i h = j
Limit for "j" is 0.120 - 0.950.
Step 9.
Before tightening harness connectors PL3 and P4, be sure that keyways in harness connectors are
aligned with keyways in component connectors.
Step 15.
Refer to manufacturer's procedure for diagnosing and replacing harness.
Step 20.
Refer to manufacturer's procedure for diagnosing and replacing harness.
G-120
