Minimum wire harness for engine operation?

[CrankyOldMan]

Just a quick update on ECU connectors.

E7 (26 pin) is required, as it connects the injectors, ignition coils, crankshaft and camshaft position sensors, and oil control valve (VVT-I). It also connects the idle air control valve and VSV (EVAP) coil.

E6 (16 pin) is required, as it connects the MAF sensor, throttle position sensor, knock sensor, and primary oxygen sensor. It also connects the engine temperature sensor (may be needed for warmup/idle) and some unneeded things: max hot/foot mode sw, power steering pressure sensor, vapor canister pressure sensor, and a few others that I can't track down at the moment. The secondary O2 sensor is connected via one of the internal wire-wire connector blocks, but it may be optional as well.

E5 (12 pin) is only required if the ECU requires speedometer input, or if you have an automatic transmission (ewww!).

E4 (22 pin) seems to be optional for everything except the combination meter, unless the BATT signal on pin 1 is something other than battery voltage sense.

Also got some info on the diagnostics, since it's NOT CAN-based OBD-II. It's M-OBD on pin 7 (SIL) and uses a different protocol--possibly covered elsewhere in the forums.

[CTScott]

Originally Posted by CrankyOldMan

Just a quick update on ECU connectors.

E7 (26 pin) is required, as it connects the injectors, ignition coils, crankshaft and camshaft position sensors, and oil control valve (VVT-I). It also connects the idle air control valve and VSV (EVAP) coil.

E6 (16 pin) is required, as it connects the MAF sensor, throttle position sensor, knock sensor, and primary oxygen sensor. It also connects the engine temperature sensor (may be needed for warmup/idle) and some unneeded things: max hot/foot mode sw, power steering pressure sensor, vapor canister pressure sensor, and a few others that I can't track down at the moment. The secondary O2 sensor is connected via one of the internal wire-wire connector blocks, but it may be optional as well.

E5 (12 pin) is only required if the ECU requires speedometer input, or if you have an automatic transmission (ewww!).

E4 (22 pin) seems to be optional for everything except the combination meter, unless the BATT signal on pin 1 is something other than battery voltage sense.

Also got some info on the diagnostics, since it's NOT CAN-based OBD-II. It's M-OBD on pin 7 (SIL) and uses a different protocol--possibly covered elsewhere in the forums.

M-OBD is a Japan-only thing. The Echos did predate CAN, but were standard ISO9141 for OBD.

[CrankyOldMan]

Originally Posted by CTScott

M-OBD is a Japan-only thing. The Echos did predate CAN, but were standard ISO9141 for OBD.

So pin 7 is functionally a K-line OBD-I signal?

[CTScott]

Originally Posted by CrankyOldMan

So pin 7 is functionally a K-line OBD-I signal?

Yes - K line for OBDII (OBDII became the standard in 1996).

The 2nd Gen Yaris actually still uses it for some systems, including the SRS.

[CrankyOldMan]

Originally Posted by CTScott

Yes - K line for OBDII (OBDII became the standard in 1996).

The 2nd Gen Yaris actually still uses it for some systems, including the SRS.

So then it's a single ended signal? I found a basic description as it being 10k4 baud with 0-12V logic, using UART timing. Any chance there's a document describing Toyota's implementation/protocol?

[CTScott]

Originally Posted by CrankyOldMan

So then it's a single ended signal? I found a basic description as it being 10k4 baud with 0-12V logic, using UART timing. Any chance there's a document describing Toyota's implementation/protocol?

Toyota has some custom PIDs, but it is fully ISO9141-2 compliant for HW and SW protocol. When it first came out and code readers were $1000+, I got my hands on the ISO docs and built a code reader with one of the SW engineers that was working for me at the time. We intended to bring it to market as a low cost reader, but since we were working on it on the side, by the time we fully completed the project $100 Chinese readers hit the market.