1991 Isuzu Pickup 2.6L Auto - Transmission / Overdrive Problems

12-16-2005, 04:33 AM
1991 Isuzu Pickup
2.6L FI - 4ZE1
4 speed Automatic

Problem: No 4th gear (overdrive)

ok, so far:

i've posted on isuzupup.com, but so far, i haven't been able to solve it


from that i've heard it could be an overdrive temperature sensor, but i can't find it on the intake (where it's supposed to be), only the dash temp sensor gauge
apparently it's a somewhat common problem on isuzu's, but it's not helping me
problem: my intake (1991) doesn't match the one in the 4x4wire.com picture


also checked some of the vacuum lines, but they all seem to be correct

seems like an electrical problem to me, but i'm afraid it could be the transmission
i paid $280 for the truck, getting another trans would be like $300
and i can't use my truck for long distance driving, being limited to around 45 mph, w/out high-revs that drain my gas tank

anyone have access to tech information (wiring diagrams, vacuum diagrams) that i can use?
or does anyone know where the sensor is or how i can find it?
has anyone had to deal with this problem?

03-01-2014, 08:17 PM
Have you figured out the issue? I am having the same problem.

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