Ok, I'm new here, but I've got a lot of problems with my 99 Blazer 4x4 4-door. First, I've got the dreaded P1870 "TCC/Slippage code" accompanied by hard 1-2 shifts. Valve body, probably. Any other input on this one is welcome. Secondly, I've got some mysterious behavior going on inside the cab. My instrument panel behaves erratically, the PRNDL quits working, the temp and fuel guages drop to zero and most of the idiot lights come on. Along with this, sometimes just the security and battery lights come on, sometimes just the security light. There is no pattern I can discern just yet, it just seems to work when it wants to and quits when it doesn't. Rain or shine, hot or cold. Oh, along with this I've got the turn signal relay clicking in the backround and driving me crazy. That happens most of the time, but doesn't seem to coincide with the other electrical problem as far as a pattern goes. So what i've done so far....I checked the power at fuse11 when the guages flaked, checked ground locations and battery cables. (Looks like I could use some new ones just to be sure, but the A-----Auto storesZONES only seem to have single conductor cables. Both POS and NEG have multiple leads.I'll check the dealer(=expensive). I only found the one ground strap at the back of the block to the firewall, It looks good. Anywhere else I should be looking? Is it possible the multi-switch is bad or just wiring? I've read other places where the ignition switch goes bad too causing similar problems. Lastly, I just replaced both front hub assemblies for wear. I still have a clunk when I get near full lock when backing and turning. It sounds more like a "pop" coming from the right front wheel. Ball joints were replaced about 12,000 miles ago. Any suggestions? Yeah, lots of questions for a first post, sorry. But I need some help, my truck wont pass inspection like this. Please Help!

 

I would suspect a failing ignition switch for your dash problems. Maybe a failing multifunction (or just the hazard switch which is replaceable separately) on the clicking.

As far as the popping, if you grease the ball joints, does the popping go away for a bit? Have you checked out the inner/outer tie rods in the steering? If you grease the whole front end, does the noise go away for a bit?

 

Multi-Switch or Hazard Switch, What's the best way to diagnose it? I think i read somewhere that someone had success with cleaning it with contact spray, so I might try that as well. I'd really rather test the switches to find the fault and correct it for good. TSB#3777 points out some related things, but I can't find the full reading of it (for free) which include the diagrams.There is also doc's pointing to a possible issue with that VCM at certain pin locations of the connector. Not sure where to start, I'm handy with a meter as long as I can find out what/where to check it. The wiring diagrams in my Hanes manual are crappy, some indications aren't even correct for the given circuits. Any help on checking out the switch would be appreciated. And BTW, thanks swartlkk for the reply!!

 

Here is a thread on the hazard switch. It is pretty simple to remove. Hazard Switch

However, typically the hazard switch knocks out the lower brake lights as well. Most common with the multifunction switch is the clicking in the dash due to poor connections in the switch itself.

I am not aware of anyone here actually disassembling the multifunction switch and I can imagine it is a nightmare of springs and contacts with everything that these things do, but it may be worth a try. You could also swap it out with a switch from a junkyard for minimal investment. At the very least you get the experience of removing it on a junker so if you screw up you can figure out ways around it so you don't mess your ride up inadvertently.

As far as troubleshooting the wires and such, well, wiring diagrams will only get you so far and I haven't ever seen a good diagnostic procedure for this type of problem. I attribute that to the issue typically being in the multifunction switch which isn't deemed serviceable.

 

Thanks! Good info, great forum!! I guess I've got my project for this weekend! By chance, what do you know about the transmission problem? Most of what I've read involves replacing the valvebody/components therein. One kit had a reamer with a new piston for around $175. Anyone come up with another solution. I've already dumped $500 in this thing this week alone, before buying the turn signal switch assy. I'm driving in third mostly so far around town and such to keep the MIL off so I can pass my emissions test. Thanks again for the help and quick replies!

 

I have the same tranny issue and have done quite a bit of research. The best fix IMHO is a new VBX valve body, about $300 at TransMichigan and elsewhere,a fellow on another GMforum told me about it.It has a number of Sonnax updates (inlcuding the TCC Regulator Valve kit that requires the reamer) to stop the TCC pulsing. Some other updates I'm looking at in conjunction are the Sonnax TCC Apply Valve, the TCC Solenoid snout, the pinless 1-2/3-4 psiton kits, forward accumulator piston, Transgo shift kit and separator plate. All I need is the green to make the scene.....