Tell me all you can about P1722 CEL

[winston856]

I've got a 4EAT to 5MT swap in my '96 LGT, everything works fine except I have this stupid CEL that keeps sticking around every time I clear the codes.

LGT's only came with Auto's in '96 hence the swap, the donor car was a '95 legacy 2.2L that we took the trans and everything out of. I got a cruise control brain out of a '97 or '98 outback 5MT since my 4EAT one wouldn't work.

We converted the AT ecu to a MT and I had a P1702 code, well recently I bought an ECU for a '97 LGT 5MT and plopped it in there. Now the code I have is a P1722 which is slightly different than the P1702.

It's got to be something simiple because the car runs well, only exception is the cold start, I have to keep my foot on the clutch to keep fast idle at 1500RPM, if I let my foot off it goes up to 2500rpm's, but I can let the clutch out and push it back down and they will drop down to about 1000rpm, then I can let the clutch out and the rpm's rise up to about 1800 then settle back down to about 1100 ish. Kinda weird but I'm used to it now.

Anyway, can somebody lend me a hand here? Is it just a wire to snip or what? I've got emissions coming up pretty soon and want to be CEL free :)

[Huffer]

P1722 - Auto Trans Diagnosis Input Signal High Input

Sounds like your ECU wiring hasn't worked quite right? The 4EAT uses a separate TCU for control, and it hooks into the ECU. The main ECU might still be looking for it if the wiring hasn't been cleaned up completely?

IIRC, the main ECU doesn't care if the car is AT or MT, they're programmed for both, they just activate differently depending on what pin-out is used.

[keltik]

Ah yes this ol' issue. Do you still have the TCU in place? If you do - remove it and problem will be solved. When you release the clutch the ecu is receiving an 'in gear' signal and increasing the rpm slightly to compensate. But because the TCU is sending a 100% load signal to the ECU it rises more than it should. Disconnecting it completely will trip an ABS light.

Even in my conversion with my hacked up TCU i still get a check engine light. But i do however get a normal idle and no other issues.

[Huffer]

How did you solve the ABS light issue then?

[keltik]

I have the TCU in place but have disconnected every sensor from it except the ABS trigger line and power/grounds so it cant interfere with anything. ABS works fine.

[winston856]

What about cruise control, will I lose that if I screw with the TCU?

[Huffer]

Shouldn't, cruise IIRC is linked with throttle position, clutch & brake pedal. If you press the brake or clutch, CC should disengage. Was the same on the 4EAT.