shane1526

So i have a 94 accord with a prelude engine and transmission automatic and it is hooked up to a p28 with a hondata s300. My d4 is always flashing and it seems like my car is always starting in 2nd gear because it starts off sluggish and i never feel it shift. I am able to start it in first gear if i do it manually but it always seems to have this problem in d4. Also i tried switching the tcu to a prelude tcu but it didn't fix the problem. Any advice? Is it a transmission speed sensor or solonoid?

MAD_MIKE

Didn't think Hondata could properly control an AT, and is your P28 ECU and MT or AT one?
Most likely the reason your transmission is in limp mode is due to no communication between the ECU and TCU, when the TCU goes to limp mode it selects 2nd gear and stays there.
Use the two wire blue connector to pull the codes. If it is a code 14 from D4 lamp then that is the communication wire. Either there is fault with the wire or, unless Hondata has changed, the S300 does not support AT ECUs.

shane1526

Yah i didn't know that till after i bought it but then i went and pulled another accord ecu and tried it but d4 was still flashing.

shane1526

I was considering going with the same ecu with neptune cause i heard it works alot better for automatics. I was thinking maybe it was the speed sensor for the transmission and not the one for the speedometer. But i did also consider the fact it wasn't communicating.

MAD_MIKE

Pull the code, there are 14 codes for the TCU.

shane1526

When i had someone check the code they said it was code 11

MAD_MIKE

D4 code 11 should not cause the D4 light to lightup/blink. Not all TCU codes will cause the D4 lamp to illuminate.
Check the codes yourself. It's very easy.
Locate the two wire blue connector under the glovebox door, 94/95 cars will have two blue connectors, one a two wire, the other a three wire. You only want the two wire one.
Jumper the connector with a wire, paperclip works fine.
Turn ignition switch to II(ON)
Watch the warning lights for any blinking codes.
CEL codes from CEL lamp
TCU codes from D4 lamp.
SRS codes from SRS lamp.
And so on.

FWIW, code 11 from D4 lamp indicates a problem with the ignition coil, probably the igniter. However if this was bad I would suspect the engine would be running erratically or rough.
If code 11 is from the CEL, either the code was read incorrectly or the ECU may be indicating an overheating problem, which would cause a limp home mode(stuck in 2nd gear). Until you verify what the codes are actual(you pull them, don't rely on someone else), it will be hard to fully ascertain what is wrong with the vehicle.

shane1526

Is code 20 of any significance

shane1526

so i installed a p75 with neptune but im still having the same issue. Also idk if this is important but d4 still flashes with ecu disconnected. Ive replaced all three speed sensors and the map sensor and o2 sensor but all that did was just slightly improve acceleration.

shane1526

Anyone have any input?

MAD_MIKE

No such code from the TCU.
If from the ECU that would be the ELD IIRC.
Check your battery connections and wires.
Verify connections are clean and tight.
Verify grounds are clean and tight.

shane1526

so i figured out the problem. Currently i was running a p75 with neptune for the ecu. Well we decided to switch the wire for a6 and a11 back to the normal spots and put the accord ecu and tcu back in. After we did that all of a sudden the d4 stopped flashing and its shifting again but i am confused. To run the p75 you have to switch those two wires but i think that is what caused the shifting problem. Do you have any idea at all whats going on?

shane1526

Bump

holmesnmanny

the 94-95 honda accord obd1 ecu indeed has the a6 and a11 pins swapped versus any other obd1 honda which is why you swap them when using the p75

.:FFS TechNet : OBD1 ECU Pin out Schematics :. This is the standard honda obd1 pin out however the 94-95 accord have those pins swapped.

If it's running fine I'm not sure what it is you're asking.

shane1526

i will try explaining again. When a6 and a11 were swapped running the programmed p75 it was not shifting on its own. When i switched the two pins back to the original places and connected the accord ecu and tcu it would shift in its own. I want to know why it was not shifting so i can fix the problem and use the programmed ecu.

holmesnmanny

Sounds like the p75 ecu or the tune are bad,

shane1526

well here is the crazy thing. Just in case i decided plug in the neptune ecu again. Go figure d4 is flashing again but the crazy thing is now its shifting automatically with no problems.

MAD_MIKE

If the P75 is from an MT car then it may not be communicating with the TCU.
2nd gear is limp mode for the TCU/transmission.
If the P75 is from an AT car, you will need to verify that it is still able to communicate with the TCU properly, otherwise the TCU will just throw its hands up and go into limp mode(2nd gear).

shane1526

well its a modified auto p75 from ha motorsports with a neptune program installed. But like i said earlier its shifting now after i put the accord tcu on and switched a6 and a11 to their original spots.

MAD_MIKE

Speak with HA Motorsports and verify that the unit you have is indeed compatible with your TCU and what they suggest as a remedy.

shane1526

they were the ones that recommend it after i gave them all the details. Lol ive been talking with these guys for a long while because we had to get some issues figured out with tuning.

shane1526

do you know of any tuners in texas that are knowledgeable or familiar with the neptune program?