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Truck went into limp mode

Tiny
HENRY SEARAN
  • MEMBER
  • 1997 CHEVROLET SILVERADO
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 280,000 MILES
My transmission went into limp mode so I checked the codes and it gave me shift solenoid code. So I replaced them and it did not help. All of it started when I left it running for an hour then the next morning when I started driving it I noticed it. Please any help would be greatly appreciated.
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Thursday, August 26th, 2021 AT 6:41 PM

10 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi,

Could you let me know the codes that were found? If you replaced a shift solenoid, let me know which one it was. Also, let me know if there were any codes related to a pressure sensor or line pressure.

Take care,

Joe
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Thursday, August 26th, 2021 AT 10:11 PM
Tiny
HENRY SEARAN
  • MEMBER
  • 7 POSTS
P0141, p0420, p0430, p0785 . And I believe the first one is for my catalytic converter.
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Friday, August 27th, 2021 AT 8:33 PM
Tiny
HENRY SEARAN
  • MEMBER
  • 7 POSTS
I'll have to look up what the codes are.
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Friday, August 27th, 2021 AT 8:33 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi,

I can do that for you.

P0141 has to do with the bank 1 sensor 2 heated oxygen sensor

P0420 has to do with the catalytic converter (operating below threshold bank 1)

P0430 has to do with the catalytic converter (operating below threshold bank 2)

P0785 is the one that deals with the 3-2 downshift solenoid.

Here is what I need you to do: Clear the codes and see what codes return. If the P0785 returns, we will be looking for an electrical problem related to the issue between the VCM and the solenoid. Either we have a short to power or an open circuit. Voltage is too high or too low.

Let me know if you already did this and it returned. If you haven't, let's give it a try.

Take care and let me know.

Joe
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Friday, August 27th, 2021 AT 9:11 PM
Tiny
HENRY SEARAN
  • MEMBER
  • 7 POSTS
The code came back, but I remembered that my anti lock brake came on and stays on. Been doing that since bout 2 weeks ago.
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Saturday, August 28th, 2021 AT 1:38 PM
Tiny
HENRY SEARAN
  • MEMBER
  • 7 POSTS
Or the light has been on.
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Saturday, August 28th, 2021 AT 1:39 PM
Tiny
HENRY SEARAN
  • MEMBER
  • 7 POSTS
And I changed u joints the the day this happened or the day before. Is it possible I got something in the transmission when stabbing the drives haft back into the transmission output shift?
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Saturday, August 28th, 2021 AT 1:42 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi,

I don't feel it has anything to do with the driveshaft. Is the speedometer working properly? As far as the ABS light, that could be the result of being in limp mode.

Let me know.

Joe
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Saturday, August 28th, 2021 AT 9:44 PM
Tiny
HENRY SEARAN
  • MEMBER
  • 7 POSTS
Found it, the 3 2 downshift solenoid was melted.
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Sunday, August 29th, 2021 AT 4:10 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi,

Glad to hear you found it. If it was melted, that is where the voltage issue was coming from. Have you already replaced it and are things working properly now?
Joe
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Sunday, August 29th, 2021 AT 7:09 PM

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