348 1-4 check engine warning light

Your 348's V8 engine operates like two 4-cylinder engines. Two Motronic engine management units, two coils, two fuel pumps and filters, two throttle sensors, two crank sensors, two catalytic converters, two oxygen sensors, etc. One on each bank. You're getting a "check engine" light because the Motronic unit on your 1/4 bank has detected a reading outside the normal parameters on one of the systems that it monitors. By downloading the stored fault code/s in the control unit and checking the code against the chart, it tells you what it found, and points you in the right direction to correct the problem.

 

1. Always listen to Miltonian.
2. When the light is on, does the engine feel like it still runs well?

Recently, my '91 was running fine with the 1-4 light coming on occasionally. I tried the well worn method of turning off the battery, then turning it on a day later, starting the motor and letting it idle for about 18 minutes without turning anything on, moving it, etc. (taught to me by Miltonian). That didn't change anything, this time however, and was cutting out when the light came on after a while.

It felt like an air flow sensor problem, so I pulled and cleaned (with a electrical contact cleaner spray) the four air flow connectors on the intakes. Let them dry out ofr a day, reconnected, let idle for 18 minutes, and I'll be damned if it doesn't feel like 50 more horsepower. Oh, and the check engine lights stay off!

 

Many CEL/SDL false indications are due to poor electrical connections. Some choose to remedy the situation with the SRI Gold Connector Kit. Many threads on this.

 

Hi Tom, Jeff, or Chuck,
Can you tell me where the four "air flow connectors" are that you cleaned. Seems likely that I have a similar situation.

Now that Jeff helped me make a TEST WIRE to pull the CEL codes, I am trying to solve the codes 4121, 1211, and 1212.

Thanks in advance.
john

 

Actually I didn't clean anything, I had the SRI Gold Connector Kit installed when my 348 was in for a top end rebuild (don't ask)

Not sure if this is what you are looking for but here goes
Catalyzer temp ECU 4121
Open the rear engine hood, the cat/exhaust ECU is located under each shock tower (opposite side of the coil pack). These ECUs are a common failure point. Use a laser thermometer to confirm you do not have a cat overheat condition. If you don’t simply unplug the cat ECUs, no CEL will light up but there will be a “silent” code stored in the ECUs. Might be a writeup on this on my348.com

Lambda regulation Additive value for self adaptation (O2 sensor or coolant temperature sensor or MAF) 1211
Lambda regulation multiplicative value for self adaptation 1212
Lambda regulation intake manifold compensation (MAF or O2?) 1212 (1213?)
O2 sensors connect into a connector block located below and behind the air filter box. Ernie did a thread on getting to these. http://www.ferrarichat.com/forum/showthread.php?t=253394 and also on my348.com

The Mass Airflow Sensors are the units mounted to the air filter box and the rubber tubes that continue the airflow to the intake plenum. Pretty easy to disconnect and clean the connectors.

 

These are the sensors/connectors that I cleaned. They are VERY obvious, easy, and accessable. Just follow the large tubes from the air cleaner assembly around each side of the engine to the intake manifolds. There are twin pairs of connectors on each intake.

 

Hi Tom and Chuck,
I cleaned the MAF contacts and both O2 sensor contacts. Problem was they did not look the slightest bit dirty so I don't think it was the cause for 1211 and 1212. I didn't get a chance to drive it again but when I do and if the CEL comes back, I can start swapping the O2 sensors (can I simply swap the connectors?). Additional info here is that my red Tempurature light was coming on. It was intermittent and now it comes on sometimes immediately after start up and completely cold. I will try to clean those contacts too. Could this be the cause of my 1211 and 1212 CEL and not the o2 sensor? Can I also just reverse the wires to isolate the problem.

Code 4121: I will buy a lazer thermometer to check the cat temps. If they are not overheating is it advisable to drive with the sensor unplugged? Or do you mean just temporarily? I didn't get a chance to clean those contacts. Will try that next.

Thanks guys
John

 

The cat ECUs are a ridiculous price that I do not care to pay (at least not now). I borrowed two cat ECUs that were known to be good to confirm that mine were bad. Once confirmed I just keep mine unplugged and check the temps once in a while with the lazer thermometer. By the way, I am running Hyper-Flow cats on my car. You will have to decide for yourself if this is an acceptable practice for your car.

As for the other codes, yes it looks like you could have a bad coolant temp sensor.

Your question about just swapping O2 connectors from side to side. Ugh! Not sure I would want to be sending info from the left O2 sensor into the right side motronic and vice versa. Seeing how you have a high temp indication at startup I might be inclined to chase that avenue first.

Just my two cents.