1998 Saturn SC1 Doesn't shift after engine gets hot

Tiny
STEVENEWBY
  • MEMBER
  • 1998 SATURN SC1
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 10,200 MILES
My daughter's car wants to remain in low gear (yes, it's an automatic transmission) when she gets caught in rush hour traffic and engine heats up. She claims the RPM's are about 5,000 to go 30 mph. Is this the transmission control unit acting up intermittently? On her typical drive to work or class she has no issues. She took it to the Saturn dealer and they took her $40 for computer diagnostics, but then said they'd need more money to determine the actual cause of the computer transmission fault code. It's an old car and we don't want to spend a lot to repair it. How much is a new TCU? Is it something I can replace for her?
Her Dad
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Friday, October 24th, 2008 AT 5:58 PM

3 Replies

Tiny
MASTERTECHTIM
  • EXPERT
Go to autozone and have them scan the computer for codes. They do it for free then get back to us with the codes and we can go from there.
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Friday, October 24th, 2008 AT 6:46 PM
Tiny
STEVENEWBY
  • MEMBER
Per AutoZone:
P0732 gear 2 ratio incorrect
P0733 gear 3 ratio incorrect
P0734 gear 4 ratio incorrect

Could the transmission be slipping? Only when it gets hot? Based on the RPM's per my daughter's observations, she wouldn't get close to 5000 RPM's at 30 mph even in low gear if it wasn't.

Transmission fluid level appears normal and car regularly has oil changed and fluids topped off at Saturn dealership.
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Tuesday, October 28th, 2008 AT 6:41 PM
Tiny
MASTERTECHTIM
  • EXPERT
Its definitely possible for a slipping transmission to be causing your problems but its also possible a bad shift solenoid or input sensor or a broken power wire going to transmission. Definitely stop driving and my suggestion is to take it to a trans shop for diagnosis. This is tricky for a tech to properly diagnose so I wouldnt wanyt you to go down a wrong path, the diagnosis usually wont take longer than a hour.
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Tuesday, October 28th, 2008 AT 6:53 PM

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