Barbary

So the situation is my check engine light, intermittent, came on only for the 2nd time since I've had the car. I don't have much experience w the code stuff. What I'm going to have to do is tell a mechanic up here how to check and read the cars OBD-1code when they only work w OBD-2's. I do know it has something to do w the code flashing a certain number of times
If some one would run down the procedure for me so I can tell the mechanic

I put in search "check engine light" but only came up w strange stuff___I don't do these things well
Thanks

Arsenii

Hello,

Here is a detailed post on the process of retrieving codes from the OBD1 equipped vehicle, and a complete list of codes that come along in those systems. If you need a little more detail out of the ECU, there is also a way to get Engine Live Data out of it as well, here is how to do it, though the drawback is that refresh cycle, or the time it takes to refresh the given information, like engine RPM and MAF readouts, is about 1 second, an inherent limitation of older systems.

Hope this helps and best of luck!

KahnBB6

iTrader: (5)

^^ Joe, Arsenii forgot to link the relevant pages to show you how to do it. Edit: I'm wrong. He absolutely did. I just didn't see the hyperlink word in his post-- sorry Aresenii!

Here are the main threads on this:

https://www.clublexus.com/forums/es-...ght-codes.html

https://www.clublexus.com/forums/mai...ble-codes.html

https://www.clublexus.com/forums/per...retrieval.html

Arsenii

Oh did I really..?

I always put links in text, and considering that you are not the only one to get tricked by it, seems like a time to switch my habits..

Barbary

Thanks guys, hopping to put this valuable knowledge to good use. At a chain shop they don't do OBD1's anymore has been my experience.
makes me wonder if all these sensors, circuits are available anywhere
Really helpful to me
Barbary

KahnBB6

iTrader: (5)

Whoops!! I checked your post again and sure enough you did but I totally missed it. My apologies, Arsenii!!

I think embedding the link into text is perfectly fine. I'd only suggest making the link word bolt or underlined.

I'm sorry-- I honestly did not see it there!

KahnBB6

iTrader: (5)

Joe, it's not really that hard to pull OBD1 codes. It's just a little tedious and some consider it too "old fashioned" since you have to count CEL flashes and pauses to determine which code the computer is giving you. Also 1996+ OBD2 codes tend to be much more narrowed down and specific (especially with today's new cars) whereas your average OBD1 code will mostly point to a fault in the *circuit* that the supposedly malfunctioning sensor or component is a part of, thus requiring you to not only think in terms of testing or replacing that sensor but also ruling out any electrical fault anywhere else in the circuit.

In practice if you understand how the car's circuits work it's usually pretty straightforward to figure out what the actual issue is. But since OBD1 codes are not pinpoint precise as to exactly where and what in the circuit is causing the fault it requires old school electrical diagnosis thinking to come to the root cause of the problem.

Old 1990's OBD2 and modern 2010's-2020's OBD2 just makes that old school investigation much more of a last mile necessity since the modern vehicle ECUs and modern shop scanners can make things far easier for anyone to figure out your vehicle's issue without being an expert on all aspects of your car's specific electrical system.

...

If you are referring to the availability of various OEM and OEM-spec replacement sensors, fuses, relays and other proprietary modules for the SC400 we're still in pretty good shape in 2022.

All you need in order to pull the codes yourself is an uninsulated paperclip that you need to bend out in order to jumper two specific pins on your "Diagnostic" port on the lower dash: TE1 and E1. Keep the ends of the paperclip engaged in ONLY those specific terminals and turn your ignition key to the "ON"/"ACC" position but do not actually push it car enough to engage the starter and start the car.

Keep the paperclip connection steady. You will begin to see a series of flashes. Count them and mentally note them and jot them down. After the first flash(es) you'll have a pause, then more flashes. That will make up the first registered CEL code. Then if there are more codes registered a longer pause will accompany that and the previous flashing process begins again for whatever the next code is. Then when all the registered codes have been flashed the ECU will pause even longer and then go back to flashing the first code all over again, then the second, etc. in a loop so long as you keep that paperclip jumper engaged on TE1 and E1 at the Diagnostic port.

That's all there is to it.

So for example, as a hypothetical having nothing to do with your car's issue, If you see: Flash, Flash... (pause)... Flash, Flash, Flash, Flash........... (longer pause)........ Flash.... (pause).... Flash, Flash, Flash, Flash....... (even longer pause, then it all repeats again until you pull the paperclip jumper away)....

...Then that would mean in this hypothetical example that the first registered OBD1 CEL code is 24 and the second registered code is 14.

Now with that information it requires looking into both relevant circuits that the CEL codes pertain to but most usually it's just the main replaceable sensor or module on each circuit that would be at fault and not actual wires in the chassis or engine harness.

Or it could even be just a bad plastic connector or frayed/broken terminal wire going into that connector that needs to be replaced with a new OEM Toyota connector or terminal repair wire. That only involves a little pick tool to remove the terminal wire ends from the connector (remembering exactly the slots they will go back into-- take pictures with your cellphone for reference!) and some basic soldering and heat shrink tubing to join the new repair terminal.

A bad old connector that's broken being the cause of a fault happens with 20-30+ year old classic cars. Luckily Toyota makes it easy to fix because the last five digits of the replacement connector you'd need to order are embossed somewhere on every connector in these cars! You just append "90980-" to the front and add the five digits on your old broken connector after that. (Example: "90980-12345").

For the terminal repair wires they all begin with "82998-" and the correct ones to order for a new connector can be found by matching your connector part number in the charts found in the Toyota electrical TSRM I'm linking below.

Any Toyota or Lexus dealer will be able to order you a new electrical connector and/or terminal repair wire!

Arsenii

You're good, apologies are all mine here, you are not the first, and probably not the last person to get tricked by it.
Thanks for the advice on somehow highlighting the text, I will definitely take it into consideration.

KahnBB6

iTrader: (5)

Barbary

thanks guys w your great help read the code --- single 71. EGR valve. Its right on top looks to be one of the easier parts to replace
Even had thoughts of just permanently removing it. I'm not in a smog state (such a relief after living in California).
Not too keen on recirculating smog. Any thoughts on that? Like what would that do to the CEL and such
Thanks again Barbary

Arsenii

EGR valve is an important aspect in Engine Management System, if you were to remove it, you will also need to cut it out of ECU as well, otherwise you will definitely notice a drop in performance and efficiency. I am not sure if you have a California spec car, if not, you will have a simple membrane type valve, which is cheap enough and easy to replace, making it a proper EGR removal a more complicated procedure.

Hope this helps and best of luck!

Barbary

Not the answer, was hoping for but yes helps a lot. Last thing I want to do is open my ECU, I don't even want to breathe on it. Its been working flawlessly for 30 yrs. And yes it is a California car
Thank you

KahnBB6

iTrader: (5)

Aside Joe, at some point you'll need to re-cap your ECU. I certainly would hunt down an identical good condition example of the same part number and have that re-capped (if it wasn't already) and then have your original ECU inspected and recapped as well. It pays to have a spare ECU with any car as old as ours.

As for the EGR, it's not hurting anything being on the engine but some component in the EGR system or circuit isn't working right. It could be carbon buildup. It could be a bad EGR valve or VSV. Unlike with 1992-1997 2JZ-GE engines the 1UZ-FE has an electrically assisted EGR valve. I am not sure if it even uses an EGR VSV like the 2JZ engine does.

I'd get the parts tested and replace what is needed personally but even if you were to remove it there is no need to modify the ECU in any way. What you would do, other than using a block off plate is to insert the correct resistors into the appropriate connector terminals that are meant to plug into the EGR valve. That way the engine ECU "sees" values that keep it from throwing the CEL 71.

However I think in the case of the 1UZ-FE engine you are able to clean out the EGR valve and put it back into service. I'm not nearly as familiar with those engines as I am the JZ's but I believe that is the case.

Barbary

Thank you Kahn, being in a non smog state I would love to just remove the whole thing, or if not, clean out the valve. I've seen EGR removal kits for sale and You tube vids on how to do it. I don't have the skills or tools to do these things. At best I found a shop that would replace one for me, but haven't found an EGR replacement valve online yet. I would settle on that to get the car running right.
The other stuff is all considered custom work and there're none any where near me that do what is considered custom work. I can't tell you how many times I've been told No.

Haven't even found anyone yet to hook up those engine gauges I already bought. But the weather has been the greatest constraint on that.
There are good things about living up here, (the mountains) then there are those not so good...can't find shops to work on the car

Duck05

If you really have your original ECU then you may not be experiencing proper operation of your vehicle. As suggested, acquire a spare and have it rebuilt and then swap it in and send the original out for testing and repair.

I went through that last year when my SC300 started acting really weird on several fronts. This included hard starts to keep the car running and intermittent transmission shifts. In troubleshooting the startup issue and after replacing the fuel pump and fuel pressure valve it took swapping in the backup ECU to fully resolve the problems. Sent out the bad ECU (which had leaking capacitors and broken traces) and now that repaired unit is the backup.

The car now is performing better than I can remember especially the shifting pattern of the transmission.

I used SIA since that is their main focus. Pleased with the process and turnaround (about a week).

https://siaelec.com/product/lexus-sc...repair-return/