It is strange. The two systems are not directly related. The wiring and plugs are in different locations and they have a different power supply.
Played with the plugs to see if one was loose, nothing here. When I started it the light is just blinking away. If you give it a significant amount of throttle it sputters. If I give it just a little bit at a time it's fine. Ugh, just frustrated. New (to me) car and everything really seemed fine until this. Can't wait to get it into the shop and sorted properly...
I don't think this would be the case. The no activity codes suggest that the ECU would revert to default fuel mapping which shouldn't be so rich as to cause cat problems. Did he ever check the harness for a short in the heater power supply wires. Seems there is a lack of a pragmatic approach here. Find and correct, or eliminate one problem at a time. Now it doesn't take fuel from idle without stumbling and flashing SDL at start up. Seems every time he posts there is a new problem.
I think it's just running that rich at first start - like almost flooding itself if you give it too much gas
FWIW, my 96 starts right up, but will sputter if you give it gas right away. Wait 20-30 seconds and its fine. A flashing slow down light at start up points to cat ecu or thermocouple. I had this issue when I first got my car and ended up getting all green potted ecu's, new thermocouples, and found the bypass ecu plug swapped with the cat ecu as discussed before. No problem since.
sgtpeper was probing the sockets which corresponded to the white wires (on the car side of the harness) and earth. I assume "1" = "L" = open circuit. Although it's not clear which socket is giving what result, I assumed the first socket was open circuit (no short to ground) and the second socket was the Motronics ECU reacting to the voltage from the ohmmeter. I've seen something similar when probing Motronics ECU pins. Perhaps sgtpeper could also try putting the meter across both sockets. If this shows "1", then this would prove that the two wires are not shorting together. My mistake. I didn't realise it would revert to default mapping. Anyway, it does sound like two problems now (unless the short problem has been fixed).
My mechanic had me run one more test - he had me pull each O2 sensor plug and check the white wire one side and ground on the other to see if it was grounding out on anything and nothing was - so that is good at least. He's also recommending I pull the plugs for the rear O2 sensors and drive the car a bit to see if that causes the fuse to pop or not. He ordered some of those ECUs - but they take 2 weeks to come in. He's interested to check out that design as well.
That depends. Did you clear your codes and check to see if your heater codes came back? Is your fuse still ok? Is the burning smell still there? If your only current problem is a faulty thermocouple or thermocouple ECU then you"only" have to worry about bank shutdown. If it were my car, I'd wait until I had fixed the SD problem before driving (especially if it's giving a poor response when hitting the gas pedal). Did your tech order a couple of thermocouple ECUs for you and will he charge you for both or will he only charge you for the parts that are actually broken? (i.e. If the problem turns out to be a thermocouple or thermocouple wiring, will he he still charge you for the SDECUs from Technistrada?) My tech seems to have a shop full of commonly used spare parts for faultfinding, but I like to keep a few spares of my own, including an SDECU. It's a pity you live so far away from me.
Same, I had a couple large boxes of spares I accumulated during my ownership. SDECUs, nice used catalysts, shocks, springs, shock ECUs, shock top gears, wheels, it was getting crazy how much stuff I had. After I sold the car, it took me a few years to rid myself of everything. I think all I have left is a low miles, nice condition oem muffler/exhaust that I couldn't pass up when offered. Oh and a couple used up catalysts...
The SDECUs are powered by the same source as your fuel injectors, MAF, idle speed regulator, exhaust bypass solenoid valve, fuel tank vent solenoid, cam phase sensor, etc... Bizarrely, there is no fuse, just a Motronic ECU-controlled relay. You can check the voltage on the SDECU with your multimeter In case you have a local wiring problem (open circuit), you can check voltage with your new multimeter. It's pin A (green wire). You'll need to turn on your ignition (and, possibly, your immobiliser off). Use the 20 volts DC setting ("V" with straight lines above it) Image Unavailable, Please Login
The only code I have right nos is P1445 and the fuse has not blown again - yet He won't charge me unless I want them just to have for when another one blows. He is ordering the probes as well. He thought it was interesting that I have the slow down light but that it isn't shutting down a bank. He also doesn't think the stumble when I first rev hard is anything but a dirty valve or sensor - I forgot which. It also goes away once the secondary air pump shuts off. Remember, I'm at a mile high so air is thin here. He didn't have a good ECU around the shop at the moment as he's had to install so many lately on cars coming through.
Which O2 sensor wire should have the blue ring on it? He told me but I forgot. He said it's common they get plugged in backwards too - so I'm tracing the wires to make sure of that too
I thought that the stumble might be because a bank had momentarily shut down, but he may be right about the sensor/valve.
Ok. So mine are plugged in correctly at least. For checking the relay - which one is it and where? Thanks!
It looks like your multimeter can supply/output three different voltages. In theory, you could select 1.5 volts and put the leads on the plug going to the right SDECU to simulate a normal cat temperature and extinguish your SD light (with the engine running). Anyway, I wouldn't want you to burn your hands or gas yourself with the exhaust.
Don't bother with the relay. Your car wouldn't even run without that relay. Your fuel injectors wouldn't work. This relay ("M"/"E13" on the 5.2 car) also powers the fuel pump relay ("N"/"E2"), so no fuel at all. The relay "E" numbers are printed on the relay panel.
So would I pull each sensor individually, then start the car, run 1.5V through to the ECU, and in theory that would tell me if it is an O2 sensor that is bad? Which would then point toward the ECU as the culprit?
You're probably confusing your systems here (like I often do). The O2 sensors seem ok for now. The SD light is now the main issue (thermocouple and thermocouple ECU-related problem). The Ratarossa video I posted a link to earlier shows you how to use a 1.5 battery to simulate a good temperature signal from the thermocouple ECU (SDECU). Using a multimeter with a 1.5 volt output saves you soldering wires on a battery, but you still really need a set of extension wires, pins/sockets, and crocodile clips* to make the job easier. But this would only tell you if your wiring and indication system is ok. It's just something to do until your parts arrive from New Zealand. *I bought a cheap set of jumper wires with crocodile clips on them (probably made in China) and a couple were open circuit and some added excessive resistance, so not the best buy. You have to check them with your multimeter before you use them.
ahhh got it. So it wouldn't really tell me if it's the ECU or not. My mechanic's theory is that I'm hitting some specific temp and popping the fuse. I guess I should try his idea of unplugging the rear O2 sensors and driving a bit to see if that does anything?
To do that, you could swap your main cat SDECUs. You will still get an SD light, but your code will change if your SDECU is faulty. If the code doesn't change, then your thermocouple may be faulty. Is your tech's reasoning behind the rear O2 disconnect to see if the heaters in the O2 sensors are shorting at high temps? When you found your wiring damage, was there more than one wire with insulation missing? You don't seem confident in this being the cause of your blowing fuse.
I think anything is possible for the fuse blowing. It looked like it had been exposed for a while though - it has a decent amount of oxidation. Only 1 wire was exposed. Yes, that is his idea, to see if the O2 sensors are shorting at high temps after a longer drive - as in about 30 miles when I would get a check engine light.
My money is on the flashing SDL on startup being a bad cat ecu. Swapping it around with the bypass ecu will probably move the code and makenit turn into a delayed check engine light after some drive cycles. Now the blown fuse is another matter. The exposed wire is certainly a problem point. I suspect potential other wire harness issues. Maybe some damage due to getting main harness hung up while doing an engine out? Anything is possible. I'd want a trio of known good ecus to start with to remove that from the equation and focus on whats causing the O2 and drivability issues. Out of curiosity how do the long term fuel trims look relative to each other across banks.
