Check engine light came on my 2002 3.0 Stype. I scanned it and got a P0430 & P1233 codes. Below is freeze frame data for it.

Fuel system status: Bank 1 closed loop, Bank 2 not reported
Calculated load 39%
Short term fuel trim Bank 1 -0.78%
Short term fuel trim Bank 2 5.56%
Long term fuel trim Bank 1 -0.78%
Long term fuel trim Bank 2 2.34%
RPM 1603
Speed 34 mph

I noticed a slight stumble when accelerating at low speed after the light came on.

I got under the car and checked the o2 sensor connectors and they are tight and not corroded.

I also scanned the o2 sensors with the car running. The graph is posted below.

I'm wondering if someone can direct me as to the next logical steps to investigate. Also are the two codes related or seperate issues?

 

Well, I borrowed an infrared thermometer and thought I would check the upstream and downstream temps on the catalysts. My understanding is that the downstream temperatures should be higher than the upstream temps due to the catalytic reaction

On Bank 2 (left side) where the problem is, the upstream was 369 deg F and the downstream was 306 F. On Bank 1 (right side) the upstream was 357 F and the downstream was 325F.

Neither side is what I was expecting. Could this be screwed up due to the fact that the temperature in my garage is only about 20 deg F? The car was warmed up for about 20 minutes before measurement and was at idle when I checked the temps.

Any suggestions would be appreciated.

Thanks!

 

Have you cleared the codes and checked what came back? You did not post the mileage either? If the car has high miles I would consider replacing both cats.

Did you ever drive for an extended time with a check engine light on? People need to understand if the fuel is being burned inside the cat instead of in the cylinders it will wear and degrade the cat.

Your fuel trims don't look bad so it's pointing to a bad cat. I would replace it with an aftermarket unit because of cost. P0430 is for Bank one so focus on that side. Drivers side here in the US.

I would swap the O2 sensors from side to side to see if the code changes. If not then it strongly points to bank 1 cat.

Have the O2 sensors ever been changed?

You other code is a bit rare and related to the fuel level sender not sending data to the fuel module. Have you reset the inertia switch just in case? Probably not it but it is cheap and easy to do.

Does your gas gauge read correctly?
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Bank 2, but yes US driver side.
+1 on seeing which code comes back first after a clear.

 

tbird6 and JagV8

The car has 102,000 miles. We bought it 7 years ago at 69,000 miles. It has never been driven far with the CEL on. Don't know if the sensors have ever been changed. It's going to snow here tonight and tomorrow so I will clear the codes and check in a couple of days. Ditto the sensor swap.

Regarding the fuel sender issue. The gauge works fine and have no problem getting fuel. My wife does frequently drive until she is on fumes before she refills. Could this cause a problem? I will do the inertial switch reset.

Thanks guys I will post when I address your suggestions!

 

Yes. Pump is fuel-cooled so can overheat and is expensive to replace for such a reason

 

I agree. The fuel is the coolant so a good practice is to avoid going below 1/4 tank. But your car is running OK so I think the fuel pump is working OK but some data is not getting thru.

When was the fuel filter last changed? It is hidden pretty good on the S-Type!

My hope is the P1233 code will not return after you clear the codes. Sometimes there are random codes in memory. I know there should not be but I have seen them before.
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