Ascender 2WD V8-5.3L (2004)
Gear Sensor/Switch: Technical Service Bulletins
Engine Controls - Lack Of Power/TCC Engaged by 20mph
SOURCE: Isuzu Service News
TITLE: Lack of Power and the Vehicle Has Shifted to 4th Gear with TCC Engaged by 20MPH
APPLIES TO: 03-04 Ascender
SERVICE TIP:
Complaint:
Transmission may have quick upshifts and is in fourth gear with TCC applied by 20 mph. Sometimes DTC P1875 may accompany concern. The
customer may also describe the condition as a lack of power, chuggle, miss, shake, or surge. This condition can also occur on 2WD models.
Correction:
The ECM or PCM may believe that the Transfer Case is in 4low and change the shift pattern accordingly. Use the Tech2 to verify the status of the
4low input. If the 4low input status is "YES" or "ENABLED" with the Transfer Case in 2wd or 4wd High or if this is a 2wd vehicle then the 4low
signal circuit is shorted to ground. This could be caused by the 4low circuit being shorted to ground or the TCCM and/or ECM or PCM is taking the
circuit to ground.
Step 1
Disconnect the TCCM "If Equipped". If the concern goes away, replace TCCM. If concern is still present go to step 2.
Step 2
Remove 4low signal circuit from ECM or PCM connector and if concern goes away inspect the 4low signal circuit for being shorted to ground. If
concern is still present with the 4low signal circuit removed from ECM or PCM connector, then replace the ECM or PCM.
