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Service Engine Soon...!?!?!?


xtremerevolution

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1995 Buick Regal L27 (3800 Series I) w/ 4T60E. Transmission was rebuilt 8,000 miles ago.

 

So I'm driving down the highway today and I swerve a bit into a ramp that goes from one highway to another. As soon as I make that tight turn, the "Service Engine Soon" light bulb turns on.

 

Symptoms:

 

- No 4th gear

- No overdrive

- No automatic downshifting

 

By no automatic downshifting, I mean if its at 15 mph in 2nd gear and you floor it, it won't downshift into 1st gear.

 

However...if you manually pull down the shifter into 1st gear, it will downshift into first. Otherwise though, it doesn't downshift into **any** gear. It shifts up to any gear just fine though. This pretty much means that if you're at 30 mph in 3rd gear and you floor it, you'll accelerate in 3rd gear. Usually at 30 mph at WOT, it will quickly downshift into 1st.

 

At least the car is drivable.

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Check the easy stuff, fluid level, vacuum line to trans, electrical connectors on trans. How long since trans was rebuilt time-wise, still under warranty?

 

Trans is fine. I had a shop plug it into a scanner.

 

TPS (Throttle Position Sensor) is out of whack. At idle it reads 2.8 Volts. It should be reading less than 1 and 5 volts at WOT.

 

So I'll change that out when I get to changing the gaskets.

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