klite24

Hi guys! I've been having tranny problems with my 5th gen for like eternity. Anyways, this morning I tried to pull a code and it came out code 15, D4 blinked 1 long and 5 short burst. Searched the web and it says problem with the TCM/TCU. Is this correct?

The tranny before when put to reverse, wont engage, you need to rev it from 2k to 3k before it engages. Also, upshifts from 1st to 2nd and 2nd to 3rd revs up to 3k-4k before shifting. I already did a 3x drain and refill, changed the shift solenoid and cleaned both countershaft and mainshaft sensors. The other day, I did a ATF dialysis, and the reverse now engages after 2-3 seconds. Problem now is the upshift. TIA

MAD_MIKE

Code 15 is for the NM sensor located on the right side cover of F22 ATs.
You will need to check that the wiring is not damaged, if it is fine then check that the resistance of the sensor is 400-600Ω @ 68°F(20°C). If these two items check out, most likely the sensor is coated in ferrous material and needs to be wiped clean.

Pull and clean #15 & #16 replace the O-rings. 10mm wrench. They will be stuck pretty good.


FWIW
NM/NC sensors are magnetic pickups, or Hall effects devices. These two sensors monitor the shaft speeds inside the transmission for input to the TCU or PCM which then will command an upshift. When the clutch material wears it also wears the steel discs inside the transmission clutch packs. This steel is suspended in the fluid until it settles to the bottom of the sump, attaches to the magnet on the drain plug, or attaches to the magnetic ends of the NM/NC shaft sensors. If the NM sensor is setting a code the NC sensor is probably just as badly coated. When the layer of material builds up on them sensor resolution is lost and the TCU no longer receives a signal.

klite24

Thanks for the reply. I was able to borrow a TCU, and after installing it, I checked for codes prior to starting. D4 flashed 1 long & 3 short burst so that 13 right?

Also, prior to reading your reply, I've searched for Code 15 and found that it refers to kick down switch shorted while code 13 refers to Main shaft speed pulse generator open or shorted? After reading your post, I got confused.

Here's the TCU codes I got for this thread: https://honda-tech.com/forums/honda-accord-1990-2002-2/90-93-accord-obd1-cel-codes-2630683/
TCU Codes:

1-Lock-up solenoid 'A' circuit open or shorted.
2-Lock-up solenoid 'B' circuit open or shorted.
3-Throttle Position Sensor circuit open or shorted.
4-Vehicle Speed Sensor open or shorted - No signal from speedometer.
5-Shift Lever Position Switch circuit shorted.
6-Shift Lever Position Switch circuit open.
7-Shift Solenoid 'A' circuit open or shorted.
8-Shift Solenoid 'B' circuit open or shorted.
9-Counter shaft or transmission speed pulse generator open or shorted.
10-Coolant Temperature Sensor open or shorted.
11-Engine RPM (Ignition coil signal) open or shorted.
12-(No code 12 used)
13-Main shaft speed pulse generator open or shorted.
14-Linear (line pressure control) solenoid open or shorted.
15-Kick down switch circuit shorted.

TIA

Fitz Williams

iTrader: (1)

It sounds like cleaning the NM/NC sensors would be a good maintenance item to do when you change your trans fluid. Can't be that hard or cost that much.

klite24

Cleaned both NM/NC sensors and also the shift and lock-up solenoids. No more codes, though tranny wont shift past 1st gear so decided to change the tranny itself. Will be doing it on the 26th. Thanks guys for the help.

MAD_MIKE

With 'kickdown switch' and 'linear solenoid' that appears to be related to the later '98-'02 ATs which are a different beast from the 90-93;94-97 ATs.

This is the list applicable to 90-97s.


When you said 5th Gen I am under the impression you have a USDM 94-97 CD Accord, is this true?

Are you retrieving your codes from the D4 light?
What model/year did you borrow the TCU from?

From what I know 90-97s(CB/CD) do not use code 12 or 13 for TCU. And 98-02(CG) cars use 13, but 14 and 15 are different from 90-97s.

98-02 code revisions.
13. Main shaft speed pulse generator open or shorted.
14. Linear (line pressure control) solenoid open or shorted.
15. Kickdown switch circuit shorted.

Put your original TCU back in to the car and retest.

And please clarify what region, sub model, and year your car is, and what region, sub model, and year the donor TCU came from.

klite24

Sorry for the confusion. Anyways, its a 5th Gen 97 model Accord VTi-S, with PH222 engine VTEC. Im from the Philippines. The borrowed TCU also came from a 96 model 5th Gen VTi PH22 VTEC. The difference between the two models are more on accessories like the VTi-S came with rear sunscreen while the VTi does not have one.

Yes, I was retrieving the codes from the D4. As I've mentioned earlier, When I cleaned both NM/NC sensors including the shift and lock-up control solenoid and plugged-in the original TCU, all the error codes were gone. I think the problem is more on the mechanical side because whenever I start it up, I hear a whining sound were the torque converter is located, so I've decided to get a used JDM tranny to replace my current one.

Thanks for all the inputs. Happy Holidays!

MAD_MIKE

Philippines received the stamped 'PH22' which is similar to the Japan/US F22B1 which has a cast 'F22B1' on that same pad.
If the NM/NC sensors had a lot of crud on them, and the TC is starting to whine, most likely the sump in the transmission is plugged with that same metallic slurry. The whining is the pump running dry due to a clogged pickup.
Common problem on high mileage H4A ATs that do not have the fluid changed regularly. When you drain the transmission albeit the drain plug will be covered in that same metallic slurry.

cohesion

Sorry to bump a old thread (There hasn't been a lot of support for these sensors on forums). But I'm having mine go off at 15. NM mainshaft speed sensor.
TCU codes for honda 1990-1993 accord are different for 13-15:

13. -
14. Off Fas Fire, PGM-FI unit
15. Off NM Speed Sensor.


Mine is going off on "The Mainshaft Speed Sensor (NM) TCU code 15." Now there has been some great confusion in regards to the part number. It can only be solved using hondpartsnow.

Anyways, I wanted to replace that part with another part I got in the mail. Except the part they gave me was the wrong part. The green connector is for the Countershaft Speed Sensor (NC). Indicated by the charts on these hondpartsnow. And indicated what I personally saw on my car.

So when I took out my Mainshaft Speedsensor TCU code 15. I had tested the ohms. It was in range, it was about 480. I also tested the voltage with the battery on (to the power connectors of these sensors), and the key put in the start position. I tested it and I got ground and voltage. I did wipe off the dirt and grime on top of the sensor. According to the troubleshoot guide I look at. If it has metal dusting on top of the sensor it could interfere. But when I look at this thread. I discovered new information.

"These two sensors monitor the shaft speeds inside the transmission for input to the TCU or PCM which then will command an upshift. When the clutch material wears it also wears the steel discs inside the transmission clutch packs. This steel is suspended in the fluid until it settles to the bottom of the sump, attaches to the magnet on the drain plug, or attaches to the magnetic ends of the NM/NC shaft sensors. If the NM sensor is setting a code the NC sensor is probably just as badly coated. When the layer of material builds up on them sensor resolution is lost and the TCU no longer receives a signal." -Mad Mike

When I pulled out that sensor there is indeed a magnetic circle tip. I don't remember any metal pieces on top of this when I pulled out. But when I was doing this I had limited information. I didn't know to check. But it would probably be obvious.

Anyways, these parts are hard to come by. And hard to find. And on top of it I was sent the wrong part. The green connector. Which was not even pictured in the listing.

From what I'm gathering even so on another thread is that:

"I've had a few of those problems wind up being poor connections at the couplers. You can remove it from the trans tail housing and clean all the crud off of it.
If my old memory is working, those wires also go thru a multi-pin connector on the top of the passenger side fender well." -Hondadude

So what I am gathering is that I could just take my old one and try to put it in and see if the error code goes away on my TCU. I have 3 TCUs. On 2 TCUs I got code 15 and my car wont go past 20 mph. And on another I get code 7. And it will drive past 20 mph (Even though this TCU has a bad transistor and D4 solid and slight acceleration not powerful on stops and gos, and slight incline need to press on gas). (There is long story involving that)

Another question I have is when I'm comparing the two.
The
Mainshaft Speedsensor TCU code 15 (grey connector)
Countershaft Speed Sensor (NC).code 9 (green connector)

They both have the same wires. They both line up the same were the bolt goes in. They both have the magnetic circle piece at the end. Is it possible Honda just made two exact same sensors that work exactly alike? And decided to use a green connector on one of them?
Because I'm assuming the only way to differentiate the two is that one has a green connector and grey connector. Are their internals the same?