AT LAST! Further to my thread on March 14th.

FINALLY, my long awaited appointment with the Chevy specialists arrived this morning to do a code read on my CEL.

It came up as P1870 - Transmission Component Slipping.

The report better describes my attempt at what had happened. it says, quote "If the customer brought the vehicle in for a temporary harsh 1-2 shift & no driveability concerns are seen during a test drive, then remember that a harsh 1-2 is a result of the PCM commanding maximum line pressure from recognizing a DTC P1870" unquote.

The prognosis is that there is a sticky valve in the valve body somewhere in the transmission andthis needsto be bored out & a bigger one fitted.

These guys do not have the where-with-all to do the repair themselves& have referred me to some auto tansmission shop on the other side of the city.

The problem is not terminal but since I have an extended warranty on the truck I should get it seen to as soon as.

Anyone have this problem before? I believe it is commonplace with this transmission.

P.S. I see in the report that amongst other US makes the Australian Holden Commodore also uses this box. ('96 - '99) So it's gotta be good!!

Kyle, I've just found your TSB on the subject. It makes a bit more sence now. Still need to get it fixed tho.

 

P1870 Explained should explain the code as well as give the TSB you have already seen. The link I posted appears to be dead now. The fix mentioned in the TSB is to replace the whole valve body with the revised piece, but that can be expensive. The hones and larger replacement valves can be purchased from a few places, but I can't think of them right now.

 

UPDATE!!

Finally I have got my truck into the tranny experts. They did extensive tests including a long run & NO PROBLEMS!! They have no idea why the CEL comes on. (This has happened 3 time in as many months). They say the tranny is in good nick & if it happens again to bring it directly to them for diagnosis. The CEL only came on at highway speeds when the truck had been running for a while. Presumably at optimum temperatures.

 

If you like go ahead and let someone sell and replace your transmission but here is my suggestion! Check around and see if you can find a minor vacuum leak! This can simply be the big round hose that goes from the fuel injection to the power brake hub! This is normally a push in connector which has about a 1/2 inch hose clamped on it! If there is any kink or the connector is not in correctly a leak will occur and the transmission will shift rough as though you will be thrown out of the vehicle! Try unplugging this connector and plug it back in hard and straight and maybe you will be lucky and fix your problem. If the vacuum is correct your transmission will shift better than you have ever experienced!

 

Thanks. I've been driving with this code for nearly 2 years now.

The only time the tranny has a fit & goes into a spasm is when it gets really hot & then only ever happens when driving on the motorways.

After a while the code goes away. So far no detrimental effects detected.

Having said that, I mostly use the truck as my daily driver & probably only use about 10km of motorway driving each day. (I'm 11 km from work). So the tranny does not get hot enough to create the rough change.

It's item 241 on the list of things needing done on my truck! LOL

 

Here is my experience with the infamous P1870 code! I took my 2000 Chevrolet Blazer with 97,000 miles on it into a Walmart to get a simple oil change. My blazer has been great and it was running great and everything was fine and all I needed was a SIMPLE oil change! Now I unfortunately let the Walmart mechanic talk me into doing a special oil change which included a fuel injector cleaning at the same time. Now when they finished and I went to start the Blazer, low and behold the Check Engine Soon light came on! Mistake number 2, was the mechanic disconnected the battery cable to reset the light and I was on my way! Well, as the Blazer reached the speed to change the automatic transmission from 1st speed to 2ond speed, I thought I was going to be thrown out of the car due to rough gear change! Well, i made it home and got out my trusty code checker which I bought for $49.99 on special from Pep Boys and I got the infamous P1870 code which is not included in the instruction booklet other than to indicate it is a manufacturer specific code! A little research on the internet and I see lots of people having rough shift changing with "check engine soon" and the infamous "P1870" code set! I go back to Walmart and talk to the mechanic but he said he did not do anything to affect the transmission! I ask him to show me specifically what he did and we opened the hood, he reached to the big round brake vacuum drum on the firewall directly in front of the steering wheel and grabbed the 1/2 inch vacuum hose and pulled it out and said, "that is all we did to access the fuel system to put in the cleaner!" He pushed the connector back in and we got in and did a test run down the road. The good luck is this cured the problem so it is obvious this vacuum hose was either not in all the way or it was cocked and letting a small leak of vacuum and by reinstalling it correctly it fixed the problem. I see where most transmission people give complicated tests and fixes and usually want to replace or rebuild the transmissions, but I would suggest to people to look for a simple solution such as this, as it will only cost a couple dollars if you do find a bent or broke hose or loose connector! I hope this does help people to solve these problems as I see lots of the same issue on the internet and not too many good solutions or tests to try! My result is that my oil is now changed, the fuel injectors are now cleaned, and my Blazer is now running better than ever!