The NV233 Continued
Figure 1
150 (black wire) at terminals C9, C10, D10, D12 and D13. Check and repair the ground circuits if needed. • If the TCCM has good power and ground, replace the TCCM and recheck 4WD system operation.
Code 2: Encoder Circuit Fault:
Attempt to clear code 2. If the code resets:
• Disconnect the transfer case har- ness connector. • Key on, engine off. • Check for 5 volts at transfer case harness connector terminals 1, 2, 4, and 8 (encoder circuits A, B, C and D).
o If there’s no voltage, suspect a faulty TCCM.
o If the TCCM is providing 5 volts to the encoder circuits, measure the resistance of the internal encoder circuits to the transfer case ground.
• If the resistance to case ground is less than 5 ohms on any of the internal encoder circuits, replace the encoder/motor assembly. • If the resistance on the internal encoder circuits is greater than 5 ohms, check the resistance of cir-
cuit 1554 (black/yellow wire) from TCCM terminal C9 to the encoder/ motor connector terminal 3.
o If the resistance is less than 2 ohms, replace the TCCM.
o If resistance is 2 ohms or more, repair circuit 1554 as needed (figures 1 and 2).
Code 3: Motor Circuit Fault
Attempt to clear Code 3. If the
code resets: • Check the 20 amp 4WD fuse (fuse 19), located in the instrument panel fuse block.
o If the 4WD fuse is blown, repair the circuit as needed.
o If the 4WD fuse is okay: • Key on, engine off. • Move the 4WD selector switch between 4HI and 4LOW positions, and measure the voltage at encod- er/motor connector terminals 6 and 7. The voltage should alternate from positive 12 volts to negative 12 volts each time you move the selector switch between 4HI and 4LOW.
o If voltage alternates from pos- itive to negative, replace the encoder/motor assembly. o If voltage doesn’t alter-
nate from positive to nega- tive, check the motor control circuits going back to the TCCM.
o If the motor control circuits are good, suspect a faulty TCCM.
Fault
resets:
Code 4: TCCM RAM/ROM
Attempt to clear code 4. If the code
• Key on, engine off. • Check for 12 volts at TCCM termi- nals C6, C8, D14 and D15. • Check the TCCM ground circuits at terminals C10, D10, D12 and D13. • If the TCCM power and ground cir- cuits are okay, replace the TCCM. The vehicle used for this exam-
ple was a 1996 Chevrolet Blazer 4.3L equipped with a 4L60E transmission and a NVG233 transfer case system. Refer to the four-wheel drive system connector terminal identification chart and specific wiring schematics for your particular vehicle. Some scan tools just can’t under-
stand what the TCCM is saying. But there are still ways to hear what it’s say- ing… if you know how to listen.
Encoder Motor
Figure 2
36
Figure 3
GEARS May/June 2010
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