mre2000

1998 Lexus ES300 6 Cyl

I've had this nagging p1410 EGR position sensor issue for years. Very intermittent. Always comes back when I'm ready to smog the car. Now light won't go out, each time I reset with my scanner, it lights back up after a drive or two. A few things already done:

Position sensor tests properly at static, with power on, and at driving speed.
EGR valve operates normally when vacuum applied, so its not stuck. Can almost stall it out by applying vac directly to EGR.
Vacuum valves must be working properly since the output signal acts correctly while driving (back probed the sensor to a dvm inside the car, monitored while driving)

SO... I'm guessing it must be an electrical problem, perhaps signal not getting to the ECU.

I was trying to trace out the wires via the wiring diagrams in a fairly useless Haynes manual. Not much help. Found the yellow wire, cannot locate the White/Green. Brown wire (VCC) must be okay since I have voltage on the yellow wire at the ECU.

Does anyone know where I can find ECU pinouts for this vehicle?

I actually pulled the ECU today and found a fair amount of motor oil inside. I don't think its conductive, and I'm cleaning it up with alcohol but is it possible that the signal is compromised perhaps enough to keep the CEL on?

Pin outs would solve a lot of problems. Thanks folks.

LeX2K

Check your PM.

mre2000

Problem solved. The oil isn't conductive but rather acts as an insulator compromising connection between pin and socket. The oil is apparently PS fluid, when the PS pressure sensor fails PS fluid leaks through the connector and the pressure pushes it through the harness all the way to the ECM. Cleaned up the connectors with some alcohol and compressed air and now working like a champ. Gotta replace that pressure switch. 4 years I've been screwing with this.

jackpapa

Hi thre, I'm looking for ECM pinout and connector locations for 1998 Lexus ES300, the ECM is 89661-3T310, I have found bunch of ECM pinouts but none for this particular ECM, can someone please help? Thanks a lot.

Some background information on this, I have a persistent code P1780 which relates to the Park Neutral Position switch. However I have checked the switch itself, tested all its pins on continuity, and the immediate connector to it, all is fine. I know the next step is to check ECM NSW pin to ground voltage when shifting gears, my understanding is when in P or N, it should read 0 whereas in other gears it should be between 9 to 14 Volts. I also read the NSW should be a black with ****e strip but could not locate the correct one. The car is running fine with only P1780 that I'm trying to get rid of, mileage is now at about 196k.