The P1811 code is one of the most common codes for transmissions in 1997-on GM front wheel drive vehicles. Symptoms of this code include a check engine light illuminated and harsh shifting. Cycling the key on and off may cure the harsh shifting until the criteria for the code is met once more. We are going to cover what causes the code to set and repair options.
Code Criteria
If a shift into any gear other than reverse and forward engagements takes longer than 0.65 seconds to complete, code P1811 will set. The Powertrain Control Module will then command maximum line pressure inside of the transmission, resulting in harsh shifting. The PCM will also command the check engine light or service engine soon light to be illuminated when P1811 is set. Basically, the PCM is sensing a slip, and is increasing line pressure to maximum in order to prevent the transmission from hurting itself further.
Repair Options
In 2002, GM release a technical bulletin for the P1811 code. See the bulletin by clicking this link http://bit.ly/P1811_Bulletin. The bulletin states that a mechanical problem in the Pressure Control (PC) solenoid, contamination in the valve body, or incorrect fluid level can cause the P1811 to set. Those problems could definitely cause a P1811, but what they failed to mention in the bulletin is, what exactly is the PCM looking for when setting P1811. It's looking for a slip of 0.65 seconds or longer to set the code. See http://bit.ly/P1811_Diag_Tree. So it's not as cut and dry as the bulletin makes it to be. A burnt clutch pack, stripped overdrive clutch hub, worn accumulators, worn valving especially the actuator feed limit valve, and just high mileage can all cause this code to rear its ugly head. All of which would require transmission disassembly to repair. Now I'm not saying that P1811 is going to require a major transmission overhaul every time a vehicle comes into the shop with the code. I'm saying that it is not always going to be as simple as just changing out a solenoid.
How to Know if a Solenoid will Repair the Problem
It is impossible to know for sure what the internal shape of a transmission is while the transmission is still in the car. The first thing to check is the transmission fluid. If the fluid level is low, add automatic transmission fluid (ATF) until full. Remember that transmission fluid needs to be checked while the engine is warm and running with the shifter in the Park position. After the fluid level is OK, drive the vehicle to your nearest People's Transmission certified shop to have it checked. If the fluid level was low, there is a leak somewhere that has to be repaired. The shop will then test drive the vehicle while monitoring data on a scanner that is communication with your vehicle's PCM. After that, the shop will most likely recommend a pan drop to see if any contamination is being produced inside of the transmission. If contamination in the form of clutch material or metal is present, then a solenoid replacement will be a waste of money. If the pan is clean, fluid is in decent shape, and the mileage is below 80,000 miles or so, then maybe a solenoid will fix the problem. The thing to remember is, if the shop recommends a solenoid, then they are looking out for your best interests. It still may not fix the problem, but from what they have seen during their checkout, a solenoid replacement is worth the gamble. If the shop recommends a transmission overhaul, ask them what they found that makes them think that is the only option. Don't like what they tell you? Then call The Transmission Guy at Peoples Transmission. 1-888-415-2098
14 comments:
This blog on has helped me in getting additional information about Automatic gearbox repairs and also helped me see big picture context, which is valuable.
Great blog. I got a transmission flush in calgary and it was nice to have my car running great again. Keep posting.
So, could a transmission flush alone fix this code problem?
Could the code be caused by a bad transmission mount?
Since the hard shifting is caused by the Powertrain Control Module, which I assume is controlled by the car's computer, I'm wondering if there has ever been a computer firmware or software update that addresses the hard shifting. Can the hard shifting do more harm than the malfunctioning solenoid or valve body? Have P1811, 2003 L300 3.0... Thanks
Yeah these old models by Pontiac and Chevy are very awesome and very powerful. I love these all models with long shift. Nice work done on this blog, its according to my interest. However if you want to check the Vin of your car so side a look on saturn vue vin decoder.
I am very amazed by the information of this blog and i am glad i had a look over the blog. thank you so much for sharing such great information.transmission replacement
i wouldn't say enjoy driving in the traffic but it's one less hurdle to handle the traffic. woman are terrible drivers afterall.
Audi Transmission
Great article!!
Possibly but as the tech bulletin states,it is shifting hard because of a detected slip between gear shifts by increasing the in line fluid pressure..basically the pcm is assuming the slip (long shift) is due to inadequate fluid supply thus it is increasing the pressure to help get more fluid flowing. So a firmware or software rewrite could definitely adjust the hard shift by overriding the fluid pressure increase, however this is basically stopping something that could be helping the transmission save itself. In other words possibly cutting off a head to cure a headache. I prob wouldn't mess with any native programming in the pcm as it can invite other more serious probs.
A trans mechanic found the P1811 and told me I needed a new transmission.
Skeptical as I was and unable to afford a new transmission, I did some research online. I have the 4T65E transmission. I figured the simplest thing I could do was to drain the pan and replace the filter. I replaced with Dexron VI, the synthetic fluid. My problem was after 3-5 min of running JUST FINE, the transmission would not go - in any gear. If I turned the car off for 3 min or so and started it again, the tran. would go and shift just fine for a few min. and the same thing would happen. That led me to believe the filter was badly clogged and definitely needed a change. Changing the filter worked in my case - so far - no problems to speak of. - SO, a rebuild is NOT necessarily the answer. Check the simple things FIRST!
thank for the info
noteven the women can drive better then a guy bro my respect. for the women
ok, i dont know if ill get a response asap but its worth a try. i was wondering what damage would occur if the wrong transmission fluid was used? the run down... i have a 05 buick rend' i bought august of 2020 with only 94,7?? miles on it. it was in pretty great shape other than flex pipe needed repair. ive kept it up with basic maintenance; oil changes, tune up, new tires, ect. it had never had the transmission serviced so in may 2021 i decided to take it to AMMCO. they had the car for two days and the day i got it back the guy told my husband he had put the wrong fluid in. but drained it and put the proper one. ever since then ive had problems with shifting,and it feels heavy as in its hesitating to dive at all, and cant go up any inclines more then 40 mph. MY BABY HAS LOST HER POWER! Any feedback is much appreciated. thanks
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