92 SC400 ECU Issues

[Bertman]

Hey guys! My apologies ahead of time if for some odd reason this has already been posted. I've searched everywhere for a related topic and I can't seem to find anyone who's experienced this problem on their 1UZFE. I recently purchased a 1992 SC400. The car of course has it's issues and what not. But one issue that I'm really eager to figure out is that the Check Engine Light will NOT come on at Key On Engine Off. Furthermore, I cannot get the ECU to blink if I jump the wires on the diagnosis port. I also cannot get codes if I hook up my Toyota/Lexus OBD Scanner.

I'm ruling out a bad ECU for now since the car does run. I believe that since the engine does indeed run that maybe I have a bad ground somewhere, possibly the E1 ground wire is open? Does anyone have any idea where the E1 ground ends on the engine block? It just seems very odd to me that I wont have a check engine light and I cannot retrieve codes yet the engine does start up. I'll appreciate any input! Thanks!

 

[sideshow]

maybe blown check engne light globe

find the "w" pin in the ecu or sometiems in the diag plug
with ignition on u should measure just below battery voltage
and then ground the wire and see if light comes on

 

[sideshow]

maybe even find the w pin and make yr own check light using a test light
im not 100% sure but i vaguely remember some soarers might not have a check light
i might be wrong as i havnt seen a powered soarer dash for ages

 

[Bertman]

maybe blown check engne light globe

find the "w" pin in the ecu or sometiems in the diag plug
with ignition on u should measure just below battery voltage
and then ground the wire and see if light comes on

The service manual states exactly this as a troubleshoot method. I was looking at the diag plug wiring and it all just looks like a massive PITA to trace these wires. I wanted to get started on diagnosing the issue but I didn't have a test light or a multimeter with me today. I'll be going over to my storage unit on friday to get all the tools I need to begin troubleshooting this issue. Thank you for getting me in the right direction sideshow! Truly appreciate your input!

***Edit***
I'll also report back my findings if I do indeed resolve my problem. It's always good to contribute to the community with solutions to every problem!

 

[gloverman]

Does your scanner do live data and codes? Which port are you trying to communicate with? Cheers

 

[sideshow]

see that's y it costs a million dollars to get yr car looked
at by experts
really if anyone wants to try diagnose shit u need
a multimeter
an efi test light
and info or service manual

it's always a pain in the ass but u can either
get a sore ass and do it yourself
or get a sore ass when the dealer reams u

I find most guys understand me and what my work
is like after 5 days of diagnosing with no result

just use your brain and work it out in simple terms
I find to many people over complicate things

 

[Bertman]

Does your scanner do live data and codes? Which port are you trying to communicate with? Cheers

Yep. Sure does do live data. I'm trying to plug into the Diagnosis port under the hood.

see that's y it costs a million dollars to get yr car looked
at by experts
really if anyone wants to try diagnose shit u need
a multimeter
an efi test light
and info or service manual

it's always a pain in the ass but u can either
get a sore ass and do it yourself
or get a sore ass when the dealer reams u

I find most guys understand me and what my work
is like after 5 days of diagnosing with no result

just use your brain and work it out in simple terms
I find to many people over complicate things

I'll admit I do tend to over complicate things when it comes to my car since I've never really gotten down to DIY my own stuff. And yes, it's a shame that I'm a full-time Diesel Mechanic. I should really know what steps to take when stuff like this happens, but then again, they're two very different things to work on.

Now that I have this car, taking it to the shop is a big no-no if I don't have to. Mechanics don't let other Mechanics rip them off. Especially when I have the technical experience and tools to actually do most of the work myself. I just need a little guidance since I've never dealt with a 1UZFE Engine, or a SC400 at that. At first I thought about just replacing the ECU but then I got to thinking, well, if the engine runs, why would I even replace a $150 part when I haven't even troubleshot the issue first. I'd get fired for doing something like that at work, so why would I do it to myself? Thanks again for your input sideshow!

 

[sideshow]

Diag plug under hood doesn't always get u live data
U need to plug into diag plug above the accelerator area

 

[gloverman]

As sideshow said you need to communicate with the port under the dash. If you dont have a check light you will note get codes as the scanner counts the flashes of the check light circuit. You should get live data on that port. I had one like this recently and the ECU was stuffed. I accessed the ECU and probed directly into the ECU pin for the check light (W) and it didnt have an erth output. Flicked another ECU in and problem was solved. Then I had the ECU rebuilt. Cheers

 

[Bertman]

Diag plug under hood doesn't always get u live data
U need to plug into diag plug above the accelerator area

These cars came with a diag plug inside the car? Really? That's very strange. I've never seen a OBD system with a plug inside the car. I thought this was only for OBD-II Cars (96 and newer)

As sideshow said you need to communicate with the port under the dash. If you dont have a check light you will note get codes as the scanner counts the flashes of the check light circuit. You should get live data on that port. I had one like this recently and the ECU was stuffed. I accessed the ECU and probed directly into the ECU pin for the check light (W) and it didnt have an erth output. Flicked another ECU in and problem was solved. Then I had the ECU rebuilt. Cheers

That's exactly what I'm thinking is wrong. I don't believe I have proper ground going somewhere. However, you still had to replace the ECU, which is something I'm trying to avoid to do right now. Is there any way to check for codes if I'm not getting ground to pin W? Such as using a test light as the check engine light?

By the way, this morning I noticed a small puddle of ATF on my driveway. Looks like I also have a transmission leak somewhere. This car just wont stop giving me headaches

 

[Bertman]

Diag plug under hood doesn't always get u live data
U need to plug into diag plug above the accelerator area

Sideshow, you're a lifesaver!

I'm sorry I haven't been around to update, I've been swamped with so much going on around the house and what not. I finally got back around to working on the car this weekend. Sideshow, I took into account what you told me about the plug above the accelerator area & I did some research. I looked up what DLC plug I should be using on my scanner & sure enough, I needed to be using the Toyota/Lexus #2 DLC Plug! It's so funny how not even my general toyota mechanic couldn't figure this out either!!!! Definitely is making me question how good he is when working on Lexus vehicles.

But yes, I was able to communicate with my ECU & got code 25 & code 27, which I'm sure has a lot to do with my exhaust leak/bad O2 sensor making the engine run lean. The Check Engine Light is not on, so I'm thinking I probably have a dead dash light bulb. Sideshow, thank you SO MUCH for your help! Definitely save my a$$ some time, headaches, and definitely some $!