P1283 Assist

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P1283 Assist

Postby TooMuchControl » Fri Oct 16, 2020 10:13 pm

Recently installed new CATs and new A/F sensors.
Took it took a muffler shop to get new studs and bolts on the connecting flanges on the rear CATs, as there were some leaks at the flanges when I tested it after about a month of driving.

After the visit to the muffler shop, I'm getting this code, P1283 which seems to indicate a possible exhaust leak or A/F sensor issue...

Now, I took it to a mechanic, we had a look underneath, and this thing is tight.
No leaks anywhere on the exhaust. They had one guy gun the gas from inside the car while inspecting it from underneath - nothing. They could not tell a leak. Unbelievable. I was there too, I swear there is no leak on the system....

This is what I'm experiencing:

Noise OUTSIDE the truck - I swear I can't hear nothing. The truck seems quiet. Had a relative do "drive byes" if I could hear anything...nothing. Rolling away from me, the truck is quiet like a mouse.

Noise INSIDE the truck is very loud when applying gas.
When Idle in Drive or Park, there is definetely a shake, when in gear.
When pressing on the gas from a stop, the shake smooths out, but, as you put gas down to accelerate, there is a rumble underneath near the footwells, like there seems a big if not huge exhaust leak. VERY pronounced undeneath and throughout the truck.

Coasting, off the gas, you don't hear anything.
Everytime I put the gas down, it roars. Going uphill, it roars.

Should I pursue a failed CAT on Bank 2?
Exhaust restriction?
Has the muffler had an internal failure and backpressure is causing the issue?
I'm thinking this problem might be related to fuel injectors. Something to do with the noise increase with the gas being applied.

Strange thing. In Neutral - I can gun the car, and the noise is not pronounced.
Put the truck in gear, with load, it really is loud when accelerating

When I read my A/F numbers, from my cheapo OBDII, the A/F numbers are "ok"
I'm getting the normal .6 and .3V displays from them with no jumps -very steady as if the a/f is doing its job.
If these have "normal" signals, what's throwing the code?

The rear O2s dont seem to respond much. they have a very steady signal .7v when running, with the truck warmed up on the OBDII


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Re: P1283 Assist

Postby smj999smj » Sat Oct 17, 2020 4:45 am

When you replace the air/fuel sensors on these vehicles, you are supposed to erase the ECU self-learning or that code can be triggered. I would try erasing the self-learning memory and then perform and idle air volume re-learn before replacing any parts. if you suspect a bad injector(s)...which are usually pretty trouble-free on these engines...you can check the resistance of the injector(s) with an ohmmeter and compare to the specs in the factory service manual (which you can access via the "service manuals" link at the top of the page). If the parts are aftermarket, they can sometimes cause problems. I stick with only NTK or Denso air/fuel sensors and oxygen sensors. When it comes to catalytic converters and not wanting to spend an arm & leg on factory parts, I usually go with Walker or Bosal. Also, check for intake leaks, such as splits in the bellows of the rubber air ducts of the air intake, and, confirm proper fuel pressure if not done, already. Converters and/or restricted exhaust usually don't cause just this code to set, so they are unlikely to be the cause. However, if you want to check for a restricted or clogged exhaust, an exhaust back-pressure tester can be used to test the system; they can sometimes be found in the tool loaner programs at the local auto parts stores.

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Re: P1283 Assist

Postby TooMuchControl » Sat Oct 17, 2020 5:10 am

Thank you!

I installed an Eastern Cat on Driver side and a Walker on the Passenger side.
The F/A sensors I installed were indeed Denso.

Intake air leak - I did not check...but the rubber bellow..I will check them again.

What's odd, and I should have added...when the car is in neutral the noise doesn't seem to be there, it's under load, when gassing. At least that's what I think when I run it. Meaning that, if I gun it in N in a parking lot, the exhaust roar is not there. I'm thinking if it was an intake leak, it would be prevalent under those circumstances? Not sure what the difference could be between running it in D versus N is so much more different.

So, it would make sense for me to focus on the air/fuel side and not the exhaust. Ok.

I did open the hood, and the bank 2 side injectors seem "noisy". Could clogged or dirt injectors cause my issue?

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Re: P1283 Assist

Postby TooMuchControl » Tue Oct 20, 2020 3:41 pm


Took to the dealer and it was exactly that. Because the A/F sensors were reconnected, the code was simply reset and did not come back - its been off since a few days.

Exhaust noise - incredible resolve.

the hangers on the muffler were the culprit. I couldn't believe it. The mere loosening of the hangers from the muffler proved the noise (sounded like a loud roar) was simply deadened be removing them. The exhaust shop is going to attach a longer piece to the muffler and we will retest on the weekend.

This last one was mind blowing. It's as if the noise in the exhaust went down 50%. The vibrations of these rubber isolators caused the whole vehicle to shudder in idle as well. I couldn't believe it unless it happened in real time with the tech performing a couple of test drives. Nothing else was done / adjusted.

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