do you or have you ever gotten a P1870 code?

[Macgyver007]

HI all,
I have a code P1870 now in my truck and have been trying to find the source of it for a couple of weeks now. Sometimes the tranny actually slips but I reset the computer and restart and it perfect again. ????? whats up with that.

Here is a little bit of history, One day the tranny started slipping, noticed it was down about a liter of fluid, refilled it and it was fine for a couple hours, started slipping again and it was down just a touch of fluid. refiled it again and prepped for a tranny fuild and filter change.

Before the tranny fluid change I was getting codes P785, P760, and P1860. When I changed the fluid it was very dark and smelled a little burnt. (I know this alone is not good) Since then I have been able to drive the truck no prob. Pulls hard and no slip except!!! see below.

If I start my truck with the remote starter I can get in it and drive no prob. THe check engine light will come on after a couple of min. (codes P760, P785, and P1860) the next time I start my truck the tranny will be slipping like crazy. I shut it off, clear the codes and all is perfect again. After about 6 hours of driving I will get the code P1870 and it will stay there all the time. Except if I remote start it all will happen all over again.

I have been researching this for a while and came across an article that stated a bad white wire from the ignition switch. I assume this is tied to the trans somehow, anyone have any further information or wiring scematics on this or any further insight or ideas?

Just as an addendium to this and for research, if you have the code or something like it can you list any aftermarket parts you have installed and where there source of power is. See if we can find a pattern there... maybe

I have the following installed. Viper alarm/remote start combo(Fed from 2 main power wires in the main harness under colume and 1 power from a dedicated distrabution block I have installed behind the glove box), Aux lights, 2 on the front 1 on the back(direct from aux distrabution box) 4500Lbs Winch (direct from Battery) Aftermarket Stereo (standard Wiring), Stereo Amp(direct from Battery through CircuitBreaker)

[barpat96]

It sounds like to me that you have what many 97 blazer owners have. A bad ignition switch.

my problems:SES light coming on, No power when starting from a dead stop(If I shifted down to 2nd it would go) then shift to Drive when rolling

I went to autozone to get the codes which were :P0758 solenoid B, P0753 Solenoid A, P0785 Shift timing solenoid, P0740 Torque converter clutch, P1860 Transfer case contact plate D. I thought my 97 Blazer needed a new tranny and even the guy at autozone did to. but it turned out to be electrical in the ignition switch.

search this forums for more info about the switch.

The problem is carbon buildup on the metal contacts that allow different components to work when you turn the the key(I know this cause I took mine apart, cleaned them off and put it back on the blazer and it workrd fine) Replacing the switch isn't really that hard to do if you have the right tools. I also wouldn't suggest cleaning yours A new switch can be purchased for less than $100.00.

Here is some procedure to help thanks to others with this problem
Sfrid073 []
AF Newbie

Joined: Jun 2004


Status: offline
Posts: 29

09-16-2004, 11:58 AM Ignition Switch replacement procedure (Post #1)
This was originally posted by CCCD. Just some minor tweaks to the procedure by me. Hope this helps some of you. This is applies to a 1997 Blazer LT AWD.

First make sure the key is in the “OFF” position. Disconnect the negative battery terminal, and disable the air bag. Do this by removing the air bag fuse and disconnecting the yellow connector at the base of the steering column. Remember to disconnect the negative battery terminal first.

Next remove all the access panels and assess the situation. First remove the lower panel, 7mm Hex fasteners, then loosen the upper panel with 7mm Hex fasteners and torque drive (T25 size).

Now remove the lower steering wheel column cover. It has two T25 torque fasteners that are accessed from the underside. Note the two hooks on the rear of the cover. Now remove the top steering wheel cover. Two E6 series Torx fasteners (I read a std ¼ drive 3/32socket, might work, but I think using the right tools is better) are visible (see explanation below). Note the one on the driver’s side wont fall out after you loosen it, it has a lock nut to keep from falling out.
I read that you don’t need to remove the top cover, but I found it much easier with it removed. I used a Dremel tool to cut a slit just under the key cylinder. Now GENTLY spread the plastic enough to come around the approx. 0.75” Dia. key housing. It’s easier with the tilt down all the way. The rubber cover on the lower cover will hide the cut.

Next remove the small white connector from the top of the metal, key “tumbler”. Rotate the switch towards the passenger seat to remove. This gets the small wires out of the way so you can get to the upper left fastener.

Now you’re ready to remove the switch. Reverse Torx fasteners hold the switch in. These are the same kind of fasteners as earlier. They require an “E” series socket. Basically the fastener looks just like the business end of a torque screwdriver. It is an E3, or E4 socket. I found an E4 at Sears Hardware. It fit a bit loose but it worked. With some down pressure and slight side pressure they were removed. BE CAREFULL!!! Note the white plastic parts toward the front of the car. For the lower right fastener the white part goes on the outside of the black plastic switch, when things go back together.

Now go back underneath and remove the harness at the main block. Use a 9/32 socket to loosen center fastener (mine was red). There are basically three harnesses in one. The two outside ones are for the turn signals. Remember orientation of the harness block, relieves worry when you go back to install the new harness. These two out side harnesses come out from the bottom/back side of the ignition switch harness. Once loose, cut the zip ties and remove the switch.

Now just put everything back in reverse order. Connected the battery and test the switch before reassembling everything. When the air bag is disabled the air bag light will stay on.

[Macgyver007]

Hey barpat96, YOU ROCK!

Just finished installed the ign switch and I didn;t even clear the code Just started it up and the check engine light is now off. Just as a note to your instructions, the vertial external torx to remove the upper cover is E5 and the smaller ones to remove the switch in E4, Best to have them bought before you start at the job, Cost me about 2 hours looking for them in a friends car after my truck was apart. uh well, now I have them, Picked up an entire set E4 to E10 for about $15 CDN. i am going to post some pics here of the job while I still have it apart to help others on the site.

Cheers and thanks again, Who would have guessed that a bad ign switch would show up bad tranny codes.

[barpat96]

I'm Glad you got it fixed. I did read on here one time where someone actually had their tranny replaced Just to find out that the Ign switch was bad. sometimes its the simple things.

[Macgyver007]

Pleased to note, Been running the truck for 3 days now and no SES light yet. looks like it might me fixed although I don;t want to jinx it :-)

The tranny shops I have been to and People I have talked to all told me the same thing, "tranny gone". Cannot figure how this is not listed in a GM tid document somewhere. I am still working on the pics for the job just to point out where all the stuff is you mentioned in the description.

[Macgyver007]

spoke too soon, light came back on again today. this is just driving me nuts, pardon the pun

[kphilbin]

Transgo makes a shift kit made especially to fix the P1870 error code.

Check ebay they have 'em there.

More info on what causes the error code:

http://www.specialtytrans.com/specia...t60e-p1870.htm

[jls1719]

my blazer has the same problem with the trans and key getting stuck in the igintion

[jls1719]

my blazer has the same problem with the ses., trans., and key getting stuck in the ignition!

[jls1719]

yes