SES Code P1870

Chris97K1500 · April 8, 2004

The SES light came on just a minute ago. Went to AutoZone and had them scan the truck. Came back with 2 codes, both P1870, went to look it up, their computers showed it was a 4x4 Transfer Case Switch. What is this? I did have the truck in 4x4 Hi at the farm, then after taking it out of 4WD, I noticed the code a minute or so later. I just put it back into 4hi and 4lo at home and climbed a 16" wall straight up. So the 4WD still works. Any advice? Thanks, Chris

redvett · April 8, 2004

Did you get your calibrations changed for your big tires yet?

Chris97K1500 · April 8, 2004

No I have not, and yes, this was the first time I've had it in 4WD since I got the larger tires. Well I guess Wester's is going to be sooner than later! I've got $200 saved, guess I need about another $200. Anyone want to give me a loan?!? Chris

One other thing, It's going to take me a couple months to save up, in the meantime, is this going to hurt anything with the truck? Should I just avoid using 4WD until I get it recalibrated?

Jeremy WI · April 8, 2004

There are two possibilities with a P1870, transfer case switch or transmission component slipping. Transmission component slipping usually means your TCC apply valve wore into the valve body and no longer gets full apply pressure and the torque converter slips. If this is the case you would probably notice harsh upshifts

Chris97K1500 · April 9, 2004

Well after looking all over the net, this is a very common problem. Evidently the part GM uses is inferior, and over time it will wear out. It's a simple $250 part made by a company called Sonnax. The tranny place I took my truck to this morning knew exactly what I was talking about, in fact, they were test driving a 99 Blazer with the same thing. The guy came in from the test drive while I was there, said it drove like a new vehicle. They've done 6 within the last 3 weeks. Didn't have any during the winter, but the last 3 weeks it's been getting warmer. I played a little dumb, letting him tell me what typically is the problem and how they fix it. It's almost like he was reading all the info I had read last night. Made me feel comfortable letting them do the work. He also said GM's fix to the solution is to replace the whole tranny, basically trying to avoid people finding out it's an inferior part that GM should basically replace under a recall. But with as many vehicles that have the 4L60E trans, that would be alot of vehicles and lots of $$ out of GM's pocket. Should be done by Tues. $400 total for the part, labor, filter replaced, and new fluid. Chris

Jeremy WI · April 9, 2004

Doesn't superior transmission make a kit too, I thought I saw them a while back somewhere on the net. I think it was a package deal with a vette servo. A good GM dealer will just replace the valve body($500 part)

Chris97K1500 · April 10, 2004

They may make the part, but I took it to my local dealer, they wanted to replace the whole tranny. I don't like the local dealer anyways, but I found some people that have had work done by the guys I'm going to get to fix the trans. All were very pleased with the results, plus they have a 1 year 12,000 mile guarantee. Too bad it's not a manual, I know many good mechanics that work on manuals from my offroading days in my Toyota. I guess I'll know by Tuesday if they fixed it or not! Appreciate the help! Chris