As I explained in my PM, this code is an electrical fault in mainshaft speed sensor circuit (not necessarily sensor alone!).

This is good news since it means the problem is external to the trans. As PAH and I pointed out, it's either faulty sensor, connector/wiring, or TCU.

Check resistance (400-600 ohms spec) at MSS connector. If OK, disconnect harness at TCU w/ MSS wires (wiring diagram req'd) and check resistance again at harness connector. If OK, the TCU is the fault and a replacement is indicated.

If a fault is indicated between TCU and MSS, you will need to trace the wires to locate the open or short fault.

I have had to replace 2 ECU's in my 94 EX. Neither had any observable faults on the circuit boards. Replacement fixed problem (Code 9 and Code 21).

good luck

 

Thanks TexasHonda....I'll have to recheck agian.

 

Note, change in 3rd paragraph. I left out "at TCU" which made sentence ambiguous.

good luck

 

What's the chance of ecu going out?

I ran the troubleshoot once again and it all check out fine.

Im using another nm sensor and tcu i got from ebay. I'm still getting code 15 from the transmission. The shift is smooth up to 4th but still downshift in either 3rd or 2nd when letting go of the pedal. It accelerate fine and shifts. Can it be the cable or my transmission is toast?

 

If you're sure the sensor and TCU you substituted is good, the fault must lie in the wires or connector.

Note, TCU Code 15 is an electrical fault. Problem must like w/ sensor, connector, wires, or TCU.

Did you check sensor resistance at the TCU/Harness connector? This test will tell you if the fault lies in the wiring (open or short instead of expected resistance of 400-600 ohms) or TCU (resistance check good at the connector).

good luck

 

I checked the tcu connector. The ohm was the same when checking at the sensor connector.

 

The shop manual says if resistance checks good at the TCM/Harness, connector to troubleshoot code 9 (counter-shaft speed sensor). This sequence is same as mainshaft speed sensor w/ same resistance spec (400-600 ohms).

Or, the problem is faulty TCM contacts or Faulty TCM.

good luck

 

I checked code 9 and it checked out fine.

Will try another tcu.

 

Can bad motor mount cause shifting problem?

 

Perhaps a damaged electrical pin on the female connector at the TCU? Otherwise, must be bad TCU.

Sorry, but that's what the diagnostic says. Have you looked for yourself?

good luck