TCU code 15 kickdown
 

So last month me and my uncle rebuild the auto trannyin my 94 honda accord ex. It was working awesome up until yesterday. The tranny started slipping and it gave me a code 15 which is the kickdown switch circuit shorted. I checked the fluid and its not black and also did a drain and fill with honda atf z1 and also magnetic plug no metal nor scraps on there. I have done a bit of research as to what may have caused my tranny to start slipping. But i want to see if HAF experienced members can give me a bit of advice to what may have caused this TCU code. Thanks

The code 15 is a problem with the mainshaft speed sensor. Check to make sure the sensor is plugged in and the electrical connection is not corroded or damaged.

Alright cool thanks for the help. Any other areas to check in case its not the mainshaft sensor?

With that code, it is either the sensor, the wiring, or the TCU.

in the common diy thread on top of the gen tech help forum, there is a link to online shop manuals. The honda-tech site has a 94 manual as a pdf you can download for free. That has all of the information on testing a code 15.

Well i checked the sensors and they look pretty good. I replaced the o-rings and placed them back. Wiring is a bit dirty but good from what ive seen. I still need to check the tcu. Im just hoping its not tranny since i went through the hard work of removing and rebuilding it last month. Can the solenoids also cause this code as well? My car as i drive acts like it cant find the gears. Reverse works awesome but when i put on d4 the gears go crazy and then just revs like if its in neutral. Any other suggestions?

Doing a quick visual inspection doesn't mean the sensor is working properly. The visual inspection would find a broken or loose electrical connector.

The mainshaft speed sensor has two wires going to it, orn/blu and wht/blu. You can probably pick up that sensor at a junkyard for <$20 and swap it out.

To test the sensor, unplug and check the resistance across that sensor (It should be 400-600 ohms). You can also check for loose pins on the TCU.

This information is in that shop manual I referenced in my last post.

Ok well ill be able to get the new sensor tomorrow since the junkyard is closed today and i dont have the device to check resistance. I checked the tcu and removed the four screws to open it up. I did not see any loose or burned pins so im guessing its not tcu. Looking at the manual im just worried its something internal on the tranny but ill keep my hopes up and change that sensor tomorrow. Thanks for the help PAhonda ill update if any changes.

So i changed both sensors and still nothing.

Can this code come up also with the solenoids? Ive noticed that my car sometimes wont shift appropriately or at all. I turn off the car and try turning it on and will stall right away. I turn it on again and the car starts shifting again as i drove it until the same problem happens when my shifts are erratically or wont shift at all.

Did you get this fix? I have the same code.

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