Hummer H1 Service Manual page 257

5-58 Transmission/Transfer Case
Diagnostic Aids
• With a transmission fluid overtemperature DTC P1812
also set, check the transmission cooling system.
• Check harness routing for a potential short to ground in
circuit. Scan tool TFT display should rise steadily to
about 100° C (212° F), then stabilize.
• Inspect the wiring for poor electrical connections at the
PCM and at the transmission 20-way connector. Look for
possible bent, backed out, deformed or damaged termi-
nals. Check for weak terminal tension as well. Also check
for a chafed wire that could short to bare metal or other
wiring. Inspect for a broken wire inside the insulation.
• When diagnosing for a possible intermittent short or
open condition, wriggle the wiring harness while ob-
serving test equipment for a change.
• The temperature to resistance value scale may be used
to test the sensor at various temperature levels to evalu-
ate the possibility of a "skewed" (mis-scaled) sensor. A
"skewed" sensor could result in garage shifts or con-
verter clutch complaints.
• Verify customer driving habits, trailer towing, etc...
• If any engine DTCs or TP Sensor codes are present di-
agnose and clear these DTCs first. Then check to see if
the transmission DTCs have reset.
Test Description
The numbers below refer to the step numbers on the diagnostic
chart.
2.This test checks for a short to ground or a "skewed" sen-
sor.
3.This test checks for an internal fault within the transmis-
sion by creating an open.
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