This TSB involves 2003-2006 Isuzu Ascender and 2006 Isuzu I-280/i350 vehicles equipped with the 4L60-E transmission, with DTC P0894 and P1870.
These DTCs (transmission component slipping) may have different root causes. The following diagnostic tips are provided to assist in accurately repairing the condition.
- Slip speeds greater than about 400 rpm at steady state driving are usually caused by a slipping clutch band.
- Slip speeds ranging from approximately 100 to 400 rpm at steady state driving are usually caused by the TCC not applying but may also be caused by a slipping clutch or band.
- A plugged or restricted TCC apply fluid orifice (238, located in the pump) may cause DTC P0894 or P1870, especially in low mileage vehicles with less than 5,000 miles.
- A converter clutch valve (224, located in the pump) which does not have full travel of 0.5 in. or is stuck in the off position may cause these DTCs. Inspect the valve for chips, debris, nicks or burrs. Also, inspect the springs (225 and 226) to make sure they are not limiting valve travel. A spring that is not fully wound may catch in the bore, limit travel and cause either DTC.
- A cracked or leaking TCC solenoid (part of harness) may cause either DTC. Use solenoid test kit J44246 to test the operation of this solenoid.
- A cracked or leaking TCC PWM solenoid may also cause either DTC.