Check Transmission light on

Tiny
R.DUFORT
  • MEMBER
  • 2000 ISUZU TROOPER
  • 3.2L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 160,000 MILES
Greetings. Replaced transmission about 40,000 miles ago. It has overheated on me a couple of times after driving maybe 200 miles at 80MPH. Pulled over, waited an hour and then continued, no further problems (stayed under 70MPH). Most recently, the "Check Transmission" light went on and stayed on. I had transmission fluid replaced. Light immediately came back on. Drove it about 500 mostly highway miles (stayed under 70) and the light went out. Stayed out for about 200 miles, then came back on. No other symptoms, no issues. What think?
Monday, May 16th, 2022 AT 2:29 PM

5 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
Hi,

That's an interesting one. When you changed the fluid, was the cooler flushed? I'm wondering if it is an overheating issue since you had that before.

Also, have you scanned to see what codes are stored in the computer? That is where I would recommend starting. If the check engine light is on, most parts stores will do it free of charge. If you have a scanner, here is a quick video showing how it's done:

https://youtu.be/b2IJGfImVvw

Do this and let me know what is found.

Let me know.

Joe
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Monday, May 16th, 2022 AT 7:58 PM
Tiny
R.DUFORT
  • MEMBER
  • 3 POSTS
Greetings.

1) My mechanic did the fluid change, I doubt the cooler (which I did not know I had until now) was flushed.

2) Checked the codes a got: P1870

Thanks for your help.

Robert
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Friday, May 20th, 2022 AT 10:35 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
Hi,

The code indicates that when the vehicle is in fourth gear and the torque converter clutch is engaged (overdrive), there is excessive slippage. This is based on information from the input and output speed sensor.

The code can be set by things like low transmission fluid, if you are towing in overdrive, or if there is an internal fault with the transmission.

Pay attention to driving at highway speed to see if you notice any slippage when the vehicle is in overdrive.

Also, let me know if you have a scan tool that can communicate with the powertrain control module. If you do, I have diagnostics for the code I would be happy to send you. Actually, I just included them below.

Let me know.

Joe

See pics below.
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Friday, May 20th, 2022 AT 9:54 PM
Tiny
R.DUFORT
  • MEMBER
  • 3 POSTS
Greetings.

Thanks so much! It caused me to remember that shortly before the "check transmission" light went on for first time, I had to accelerate very quickly from 40 to 75 MPH on the highway and the transmission kind of "clunked" into high gear, which it had not done before. Like it had gotten caught between gears. There was one other incident more recently when accelerating that it felt like the trans "faltered" for a half a second or perhaps "slipped" into high gear. Not a clunk, but noticeable. 99.9% of the time, the trans runs just fine.

Would you recommend that I show the diagnostics to my mechanic, or will he likely have access to such?

Thanks,
Robert
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Tuesday, May 24th, 2022 AT 3:16 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,068 POSTS
Hi,

Chances are he will have a manual with the directions. However, it wouldn't hurt to print them and take them with you.

If possible, could you let me know how things turn out for you? I'm interested in knowing.

Let me know.

Take care,

Joe
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Tuesday, May 24th, 2022 AT 7:55 PM

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