Questions and Answers
Taurus Diagnostic Codes
Q. My 1993 Ford Taurus has a recurring "Check Engine Light". The codes are: 10(?), 111 - system pass; 173 - HEGO shows system always rich (rear); 177 - HEGO shows system always rich (front); 634 - Transmission Range (TR) voltage higher or lower than expected.
Since the mixture readings are from both HO2 sensors I would suspect they are operating and the problem is upstream from them. That's my problem. Where? Also what provides voltage to the TR sensor and where is it located? Any information to start me in the right direction will be greatly appreciated.
Respectfully,
RobertP.S. The "light" came on prior to: changing oil; replacing distributor cap & rotor; spark plugs and wires; new radiator. I do have some noticeable down and up shifting from OD to D. Maybe a problem with the "TR" whatever that is. Thanks again.
A. Those codes are confusing. I would clear the computers memory and drive the car and then recheck the codes. I have no idea where code 10 came from. Assuming the code 111 doesn't return you have:
173 HEGO sensor circuit indicates rich. (Rear Side).
177 HEGO sensor circuit indicates rich. (Front Side).
634 Manual Lever Position (MLP) sensor voltage out of Self-Test range.The 173 and 177 is telling you the engine is running too rich. The code 634 indicates that the PCM has detected an invalid combination of transmission ranges. What you can do is drive the car in DRIVE (D) and OVERDRIVE (OD) and see if the transmission stays in third with the selector in D or OD. If it does shift correctly, ignore the code 634.
The code 634 will not cause a rich fuel mixture so the cause is elsewhere. I would check the fuel pressure first and make sure it is within specs. You might have a bad injector(s), a bad ignition coil , a vacuum leak or a problem with the PCV system.
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