jjswenn

Hey YT,

I was doing some stuff last night on my 1995 22REC (California emissions) 4wd pickup M/T (5 speed manual/standard) and noticed that my Toyota service manual shows a pin at the ECU for STP (stop), but I do not actually have a wire from the harness side that feeds to this pin on the ECU. ECU part number 89661-35850. I have the factory service manuals (3 volume/editions) for this specific year make and model, and typically (as for other pins-wires on this harness), where there isn’t a need for a signal, there will be a blank spot (box with a slash through that pin) on the pin out diagram in the book. This pin out says there should be a wire going to that ecu pin. Now, to my knowledge nothing has been molested in this area of the vehicle by PO’s etc, and it’s entirely possible there doesn’t need to be a wire going to that pin for the given drivetrain. I’m just looking for confirmation from someone with a similar setup (manual, 5 speed, 4wd etc) that there doesn’t need to be a wire feeding to that STP pin on the ecu. My best guess is they have that pin there for different models (A/T) maybe, where the stop signal is needed. Anyway, let me know.. Thanks

rustypigeon

I have a '94 22RE automatic transmission. Mine does have a wire (green w/white stripe) going to the STP pin. The A/T needs to know when the brake is pressed so that it can disengage the locking torque converter. If this signal was not present and the wheels were locked up during a stop, it would stall the engine.

I don't have a manual 22RE to compare with yours. My wiring diagram also shows a STP pin for all ECU's regardless of transmission. I am not sure why a manual without any type of traction control device like our old trucks would need a STP signal going to the ECU. My guess, like yours, is that it is simply not needed in the manual transmission. Maybe they removed it for the later trucks?

jjswenn

yeah, I’m not sure why a manual transmission would need it. Although, I do know there’s a fuel cut system in these trucks. It’s just something I noticed and thought I’d come on here to ask because there’s lots of references.

Vman455

I checked mine; 1991 4WD/MT/22RE (federal emissions). It does have the green w/ white STP wire in pin 9 of the 14-pin connector, as indicated in the wiring diagram. Circled below, if I'm reading the diagram correctly.

old87yota

I haven't looked at any diagrams yet, but the stop input may also be used for the cruise control system.

scope103

Separate computer for cruise. That uses the NC contacts in the Stop Light SW.

The STP pin to the ECM uses the NO contacts.

rustypigeon is correct:

old87yota

Interesting!

Thanks Scope!

jjswenn

Okay, so what does this all mean? Is this to prevent brake lockup on antilock brake vehicles? It seems that some M/T trucks have the wire present. Or did some of the MT trucks come with cruise control (which I’ve never seen that)?

scope103

"Lock-up" is a thing in automatic transmissions. Once at the appropriate speed, the ECM signals the lock-up solenoid, which effectively bypasses the (power-using) torque converter. It has nothing to do with "brakes locking up."

I would think most (all?) vehicles would have the wire, just because it is easier to manufacture one harness and just connect the appropriate parts. But I wouldn't count on it; I'm pretty sure the ECM for a manual transmission is different, so it might have a different pin-out as well.

Vman455

I would bet this is the explanation. OP said his is a 1995, so perhaps this changed in later model years, or maybe California trucks had a different wiring harness.

When I first pulled apart my dash, lo and behold there were the wiring and connector for a clock just plugged into plastic nothing behind a blank. Bought a clock off eBay, plugged it in, and it works like it's always been there.