P1281: Cat Efficiency Below Threshold (Bank I)


Asked by Jan 07, 2011 at 08:29 PM about the 2000 Dodge Dakota

Question type: Maintenance & Repair

I recently took my Dakota for an emissions test in Califonia and it failed the functional test.  Didn't know that having a check engine light is an immediate failure else I would not have spent the $45 for the test.  Anyway I searched for "Cat Efficiency Below Threshold" and I keep getting P0420 for the error code.  The mechanic said that he would have to spend 3 hours to do more additional testing which would cost $90 to pinpoint the exact problem.  He told me that without testing he could only assume that the cat and o2 sensors need replacing which would cost anywhere between $700 to $1000.  I felt like I was being ripped off.  Suggestions?

12 Answers


It has nothing to do with your cats or O2's; P1281 Engine Is Cold Too Long Engine coolant temperature remains below normal operating temperatures during vehicle travel (thermostat). Sounds like your thermostat is stuck open, unless you changed it to 160* or lower

5 of 5 people found this helpful.

Thanks for your reply. The subject title is the exact error on the emissions test results that they gave me. So I'm puzzled as to what the thermostat has to do with the catalytic converter. Two separate problems perhaps?


Also, I would like to add that I had just purchased the vehicle from a private party off Craigslist. When I bought it the check engine light wasn't on that I can remember. And it's not always on (roughly 10% of the time it's not). The previous owner did tell me that it was recently involved in a front end collision and had to had the water pump, radiator, etc repaired or replaced. So the thermostat does make more sense. But why is the emissions test results giving me the "P1281: Cat Efficiency Below Threshold (Bank I)" fault? And what's the best way to tell if it's my thermostat or my cat/o2 sensors without having to spend $90 for the mechanic to rip me off?


it may also not have passed because the engine runs lean when the car isnt warmed up. car runs lean -> engine exhaust poor -> error code goes "wtf?" Change your thermostat. It's a $3 part. then unplug your battery and turn your key to on and off a few times, then leave in the on position for 30 minutes so the computer resets & the check engine light goes away

1 of 1 people found this helpful.

Ted is right, the engine not getting up to operating temp can cause that problem, but it would be running rich not lean and this can cause a cat efficiency code because too much fuel is being dumped into the engine and it can't all get burned. But the code P1281 is for the thermostat, not the cat/O2's... whoever told you that P1281 meant "Cat efficiency below threshold" is wrong. Forget about the cat for now, get a new T-stat and make sure you get all the air out of the system when you change it. The stock is tstat is 195* but you can safely run a 180* if you like, but don't go any lower or you will get this same code

2 of 2 people found this helpful.

You guys are awsome! I'll replace the tstat and give it a try. I'm still puzzled as to why the emissions report gave the wrong definition of P1281. So I'll do as you suggest first and then take it to autozone to get a diagnostic done. If codes come back then i'll deal with it from there. Hopefully you guys just saved me ~$1,000! If so, then I'll have to send you some beer money. ;)


After you replace the tstat make sure you clear the code..... Disconnect the negative terminal on the battery and turn the key forward (to start) and hold for 10-20 seconds. Hopefully this fixes your problem

2 of 2 people found this helpful.

I'll give it a try on Monday. I'll spend the $45 for the re-test and I'll report back. I'm only hoping that I don't have multiple problems (tstate and cat/o2) because the fact that the emissions report fault said "Cat Efficiency Below Threshold (Bank I)" just doesn't make sense to me if it's the tstat. If it was just the cat/o2 then I would imagine that it would give me a P0420 error instead but on the report I'm getting the P1281 + Cat Efficiency Below Threshold (Bank I) combo. If it clears up and passes then I'll paypal or western union some beer money for you guys! ;)


"rich not lean" *face palm* I'm sick today

P-0443, P-420, P-1281, The codes I was getting. When I had same prob so I changed the tstat from 160 to 195° then I pulled the neg batt termnial turned the key on and off few times and left it on for a few minuets then reconnected the batt with the key in on position idk if the t stat had anything to do with it forshure but it cleared the code & engine light is off but the engine would not idle so I held the pedel for a min then took it for a drive & had to use both feet at stoplights :( took it on the freeway for a mile & down a 35 mph road & I figure the o2 sensor recalibrated with idle control &seems to b working fine if I have further notes after tomorrows drive I'll post them as well good luck hope this helps !


Probably too late for binary 100100, but for the poor unfortunate that falls on this after a frustrating search: P1281 CAN be the result of Bank1 Sensor 1 O2 sensor. The P0171 (too lean) is the result of P0132 (previous said sensor failure) and will make the left side run too rich as the PCM compensates which left unattended will ruin the other O2 sensors and Cat, left side plugs fouled out and so on.I had a PCM that needed updating and got all kind of codes but after updating and replacing plugs, found the previous mentioned O2 sensor was destroyed, even though it was one of the first things I replaced trying to fix the error codes.Can be a catch 22. P1281 IS most commonly a thermostat or temp sensor or something like that but rarely can be the upper sensor, the following P0171 code persistent is the key to checking. If you replace it yourself, better get the specialty socket with the slot on the side or forget doing it yourself, it's jammed in a tough spot.

2 of 2 people found this helpful.

I wish I had known about the 160 degree t-stat earlier....*sigh*

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