With the help of Miltonian, I built a test wire and was able to pull the codes and reset the ECU's Code 1212 and 1211. I swapped the o2 sensors left to right and cleaned the connectors in front of the oil filter. The connectors were not that dirty. Code 4121. I cleaned the air filter housing (quite a few acorns in it), cleaned the MAF connectors, wiped down the housing inlet tubes and replace the filter with a K&N filter. I will buy a laser thermometer to check the exhaust tempuratures. The restricted air caused a slightly richer mix causing the 4121 Code?. My tail pipe tips are dark and a little sooty. I had another problem with the red temp light coming on. It would come on immediately after starting when the engine was completely cold and flash on and off while driving. The temp gauges were always correct. I cleaned those connectors too while the air filter housing was off. Took it out for a 30 minute ride and the 1/4 CEL came on 3 times but went right off. The temp light did not come on for the first 20 minutes. It came on and flashed on and off for the last 10 minutes. The overflow reservoir was down about 1/2 pint before the ride. I filled it before the ride and tightened the new cap. The last time I filled it before was in the early spring. There were no codes to be pulled after the ride. Any thoughts or help is much appreciated as always. John
Cant speak for the temp issue but if it makes you feel any better, my 1-4 light comes on once or twice for about 10 seconds about 3-4 minites into every drive. Then it is never seen again. I have had it to the dealer and they cannot figure it out. I personally think it is the thermocoupler just setting it off when the cats are first warming up. Once this happens, I never see it again. I have gotten to the point where I dont pay any attention to it and am looking to go to test pipes to eliminate the cats and the problem. Hope this at least makes you feel less alone. Good luck.
I am not that uncomfortable either if it continues to just flash on and off. I would like to find and fix the problem correctly if I can. Thanks for the support.
The switch for the temp light on the dash is separate from the guage if I read my schematic correctly. Check the switch and connection on the front (not the two on the back) of the little manifold that goes between the heads. It's just an off/on type switch that comes on at 125 deg C.
Is it ONLY your 1/4 CEL that is coming on, even after you swapped the sides on the oxy sensors? Does your 5/8 CEL warning light come on when you are starting the car, in test mode? The feeling I am getting is that one (or both) of your oxy sensors may be faulty, and may be causing a rich running condition, hence the CEL's for lambda regulation, and the CEL for catalyst temperature. I'd be careful at this point, you may have a genuinely overheating catalytic converter, not just a "ghost" light, although you should get a "slow down" light if the exhaust temperature ECU is triggered by excessive temperature. Just to be sure, are your "slow down" lights coming on in test mode? It might be interesting to pull at least one spark plug from each bank, and see if it looks like a rich running condition exists. On the unusual flickering of the water temp light, that one confuses me a bit. I suppose I would try disconnecting the wire from the sending unit, and see if it still comes on, which would indicate that it's grounding out somewhere, maybe at the twist connector at the left rear shock tower. Good luck!
Bruce, I will also take a look at the switch in front of engine. Other than cleaning the connectors and looking for loose wires what else might I do to test it? Jeff, Only the 1/4 cell comes on. Both CEL's come on when the key is turned. They both go out when the engine is started. I have never seen the slow down lights come on ever. I will check to see if they come on in test mode but can you explain "test mode". I already cleaned the twist connector in front of the left shock tower. Hopefully the laser thermometer gets here soon. I'll try the plugs and disconnecting the sending units and post the results. Thanks for the help! John
The "slow down" lights (one for each bank) should come on for approximately one second when you first turn the ignition key, before cranking over the engine ("test mode"). They don't stay on until you start the engine, like the "check engine" lights do. If the "slow down" lights do NOT come on at all, then I would suspect that someone has pulled the bulbs because of ghost signals from the catalyst ECU's. That's OK until you really DO have an overheating converter and you don't get the warning. Again, until you are sure that your converter is NOT overheating, I would be careful about driving the car any great distance. An overheating converter is very, very hot. Hot enough to glow bright red. Chances are that it would not be an issue with the converter itself, but with too much fuel being dumped into the exhaust - perhaps something like a bad injector. By the way, if you haven't pulled a spark plug before, you will need a thin-walled 18mm deep socket to get them out, not a tool that is in the average set, but one should be included in the factory tool kit in the leather case. Sorry, I don't recall - have you had this 348 for long? Do you know the service history on it?
