Slow down 5/8 light

Slow down is all about cat temps, cat ECU, and thermocouples. Messing with the diagnostic button is (correct me if I'm wrong) only for Check Engine lights.

Check (in this order):

1) did your cat really overheat and the Slow Down light is like your First Alert Smoke Detector? If the cat did overheat, you got some work to do to figure out why!

If Cat did not overheat, then:

2) Check the cat ECU's for cracked around the black plastic case where the potting is poured it. They are located on the outside of the shock towers, behind the coil packs. If a cat ECU has cracked, then odds are some moister got into the ECU and whacked it's little Italian brain. A simple test is to swap the two ECU's from side to side, and see if the slow down light moved over to 1/4. If yes, the ECU is likely the culprit. I'd say "replace", others might say fix.

3) Check the thermocouples themselves for frayed wires or anything that looks particularly nastly. Thermocouples can fail -- but not as frequently as those old style Cat ECUs.

 

Yes, that button is for checking your trouble codes. Go to this site and learn how to use that button to check them. It must be plugged in of course. http://www.my348.com/348.html It is also a great source of information on tracing down problems like these. Good luck!

 

Yes, 5-8 is the driver's side.

 

Just so you know BJ, the Motronic ecu will store a silent code. Meaning that you won't get a CEL, but if you pull the codes one will be present (4121) for the disconnected cat ecu. No worries though, the car will still run just fine with out them, as you have found out.

 

I have this on my ex ECU on one bank. Even after I sealed up the ECU with silicone, I still get the 4121 code but no lights.

 

Did you clear the codes after you pulled them??? If not that could be why it's still stored? Once you have pulled the codes, and get the series of long steady light flashes, you need to hold down the button for at least 10 seconds to clear the codes. When you let go of the button, after 10 seconds, the CEL will turn off if you have successfully cleared the codes.

 

Yes, I cleared the codes by pushing the button for over 10 seconds and I also switched off the battery for a couple of minutes and did the relearn process. The unit was originally on bank 1-4. When I swapped the ex ECU's the code went with it. Like I said, I get no slow down or CEL lights but the code is still there. Unless something gets worse, I will leave it alone.

 

Hmmm?

You could have a burned out bulb for that bank?

 

No, the slow down and CEL lights come on during startup. They go out after that. But I still get the 4121 code on which ever side this particular ex ECU is on if I pull the code. This code will set before I even start to drive. I have cleared it and checked it after idling for a couple of minutes and there it is. No Doubt said that it was a silent code and may not light up a warning light.

 

Well maybe your ex-ecu could have bit the dust completely? It doesn't give you a slow down light while you are driving right? Just the silent code. If so I think it's d.o.a.

 

It gave me a slow down light the other day for just a second but I had only started driving and had not even gone over 30 mph at that point. The engine was still getting up to temp. So you are probably right. It is probably dead. I will replace it soon. I could not find anyone that rebuilds them. So I guess that I will have to go for the new one.