Mechanics

CHECK ENGINE LIGHT

2001 Hyundai Sonata

Transmission problem
2001 Hyundai Sonata 4 cyl Two Wheel Drive Automatic 87000 miles

2 1/2 half years ago I experienced a sudden loss of power in the shifting of the gears in the transmission, like the codes that were displaying 1) Loss of Vacuum & 2) input/output speed sensor failure. Fortunately I had 2 months of warranty left. Supposedly. The transmission had to be overhauled, at there expense. What happened was a loud thud hit simultaniously when the check engine lite came on. Pay attention here closely. The transmission then hung up in 3rd gear. Would not shift into overdrive or downshift to either 2nd or 1st gear. You had to take off in 3rd gear. Also, operating temperature does have some effect on the shifting, like the next morning when I needed to use it the check engine light had cleared itself and. When I took off the gears shifted just fine, until about 5 minutes of operation then the incident would happen again. Lock up in 3rd gear and check engine light came on again. Check engine light would always be on until the engine cooled down overnight and when you activated ignition the next morning check engine light would clear. After overhaul and 2 1/2 years later it does this again. I would like to know what really is going on here. What do I do? Do I have to get this transmission overhauled again? Please advise. Thanks so much!
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Purplus
May 16, 2009.




Hi purplus,

Thank you for the donation.

When the CEL shows, an error has been detected by the engine or transmission management system.

In your case, the problem shouod be a problem in the trans control system. When an error has been detected, the PCM would go into limp mode if it is a major fault. This would explain why it is stuck in 3rd gear.

Turning the engine off would allow the PCM to reset itself temporarily till it encounters the problem and then it would go into limp mode again.

Quite often problems like this are caused by sensor failure. If internal components are faulty, it could cause slipping in geasrs and this in turn would cause the PCM to go into limp mode as well.

To understand what is wrong, get a scan done at your local Autozone or parts outlets, they provide free scans. Let me know the exact Diagnostic Trouble Code and we shall see what needs to be done.

KHLow2008
May 17, 2009.
Ok.I went down to Auto Zone and they don't do engine scan tests anymore. So, I went down to a " AAA" approved facility/with ASE certified mechanics. I did extensive explaining to the mechanic. The codes that were bearing was PO732 & PO734. They changed both input and output speed sensors and cleared all codes. Drove it 3.9 miles and tranny jerked again and " engine light " illuminated again. At this moment I am going to drive it in 3rd gear back down to the shop again, ever so gently, to see what codes may be displaying now and will let you know in 24 hours what they were and then we can proceed. I have included Hyundai Consumer Affairs at 1-800-633-5151 on my situation. I have a reference number that is related to this issue. Reference #358-9799. Now after codes scanned today they are PO755 and PO760 which are Shift Solenoid B Malfunction and Shift Solenoid C Malfunction. Not good from what the mechanic advised. Which was take it to a Transmission Specialist. Needless to say I was out $320 yesterday and still have a screwed up vehicle. Just new codes now. Please advise. Thanks
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Tiny
Purplus
May 28, 2009.
Hi
Hyundai issued a TSB on your problem Reference # 03-04-006 Date May 01,2003.
Is says wiring harness maybe the fault checking resistence and any pin damage. If none found then replace solenoids normal warranty applys.
Hope this helps

Docfixit
May 29, 2009.

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