Ptowndon

Hi Club members....... first time post here after owning my '92 SC400 since new. I have searched the forum but would appreciate some additional help. My car has the electric EGR valve (Meaning no vacuum hose connected to it). I have the famous "71" OBD1 code that I am needing to solve.

Can anyone share from the service manual how to use the electrical plug connector on the EGR to measure appropriate voltage or Ohms to make sure the EGR valve is getting the correct signal to operate correctly. I have removed the valve and it is very clean so carbon build up within the valve is not a problem. I just need to make sure it receives the correct signal.

I am also testing the EGR temperature sensor. I believe I have located the procedure for testing whether it works correctly. I appreciate your help.

Don

KahnBB6

iTrader: (5)

Here are the relevant pages for the 1992-1997 SC400 1UZ-FE's EGR system

Ptowndon

I thank you very much, KahnBB6, for the good info. I do appreciate you taking your time to help me out. And.... your reply was certainly timely.

Don

KahnBB6

iTrader: (5)

No problem. I hope you can get it sorted soon. I have been through the wringer in CA with extensive 90's EGR system troubleshooting and testing myself.

Zeke21

I've got the same issue with my 92 electronic EGR, code 71. Sometimes the check engine light stays on other times it comes on and off repeatedly during a drive. Let me know if you're able to solve your issue. I tried replacing my EGR valve with a supposedly known good working use unit but it didn't seem to make a difference. I should test both units per the service manual.

Ptowndon

I've driven it for 4 days now without the check engine light coming on. I also did the "driving test" to see if the light came on. It did not.

The best I can say is that I believe my intake ports are/were plugged. While I had the EGR valve out, I cleaned the carbon off it and I also ran a long thin screwdriver (and bendable welding rod) in through the 3 intake manifold ports as far as I could. I ended up scraping with the screwdriver all the way through the port (10-12") to the backside of the throttle plate.

If my light returns I plan to test the electrical part of the EGR valve and also dismantle the intake up to the throttle plate. I do believe that really needs a good cleaning. So far so good with the carbon removal using the long screwdriver.

KahnBB6

iTrader: (5)

^^ The clogging of those EGR ports will cause a CEL code 71 (EGR system restriction or malfunction). Eventually this affects the SC300's and with their "Y" shaped intake manifolds there are a few passages that need to be cleaned out of carbon buildup to cure the restriction that builds up over many years.

I'm not as familiar with the 1UZ-FE's EGR system but I think this was your exact issue which you cured by cleaning the passages out.

Ptowndon

Just letting you folks know my Code 71 appeared again. On with cleaning the intake plenum and testing my electric part of the EGR valve.

Zeke21

Thanks for the update.

I haven't been able to clear my code either. It still randomly comes on and off while driving....sometimes it stays on the whole drive. I'm beginning to wonder if I should change out the EGR temp sensor or at least test it. I have a California spec EGR system so the temp sensor is right below the EGR valve.

Ptowndon

You are having the same symptoms as I had early on. My check engine light finally stayed on continuously. Just for your info, I did remove my EGR temperature sensor and tested it in oil. The ohms readings were within specs.

ObSCessed

Guys I went through this with one of my sc400's when i first got it, it had code 71 on constantly, ran fine. I replaced egr valve 3 times, didnt solve it ,you know what did? Replacing the ecm! Popped a different ecm in and bam, been gone ever since, cant guarantee thats your issue, but it certainly is worth considering if you have a spare ecm to try. I think thats why I got such a good deal on the car, the previous owner also tried to fix it but couldnt figure it out and gave up. Moral of the story, the ecm could cause almost any issue it seems so check that.

Ptowndon

ObSCessed,

Thanks for the info on suggesting the ECM may be the issue. I fear that you you may be correct.

Don

perfctreig

I know my son dealt with that on his '93. Same solution. He had replaced several ignition coils, the plugs, then the ECU. The ECU was teh problem all along. It went from a limp I4 to a robust V8 again.

Ptowndon

Here's another update on my 92 SC400 EGR problem with Code 71 flashing..........

I removed the black step-motor cover from the EGR and sprayed it good with WD-40, then blew it out good with air. I applied +12 V to the "B1" terminal and then individually went to ground with each of the 4 "S" terminals. Then I did the same procedure while applying +12 V to the "B2" terminal. I could feel the motor stepping. Not sure how much each step should move the valve though, so I don't know if total movement was achieved. All I know is that the motor clicked and the valve moved.

Re-installed it and now have driven the car for 4 days with lots of opportunities for the check engine light to come on. No light!!

Only time will tell whether my motor cleaning and slight lubrication did any good. But, no light so far is good news.

Ptowndon

Letting everyone know that I'm still dealing with the Code 71 CEL. I bought a 95 SC-400 EGR valve hoping the motor would be the same as for my 92 SC-400. Sure enough it is the same. Installed the 95 motor on my 92 EGR valve.....CEL still comes on. Installed the entire 95 EGR/Motor on my car and re-routed coolant hoses to compensate for the different orientation of coolant ports. The car runs absolutely great, but the CEL still comes on at times when I am going up a hill. This tells me the problem is related to a decrease in manifold vacuum or possibly a change in engine temperature. Sometimes I have to drive 60-80 miles for the CEL to come back on.

Just saying I have not solved the problem. But for others with the older SC-400s, you might consider using the newer EGR valves which can be found at a more reasonable price. I still have not changed my ECU to see if that is my problem.

Your thoughts are always appreciated.

Ptowndon