1993 Blazer. Speedo off, no odometer, no cruise...

[MrFleming007]

Hey everyone!

So, I'm trying to troubleshoot a couple issues with my 1993 K1500 Blazer. The speedometer reads a constant 4-5mph fast at all speeds and the trip odometer appears to be dead (actually, it may have registered about 1/10 mile over the last couple hundred miles). And finally, the cruise control is inop. I've done the standard diagnosis on the cruise and eveything gets voltage when it should now (after replacing both the multi switch and brake switch), so I'm left wondering if maybe the vss is bad? Transmission seems to be shifting fine, but I can't confirm at this point if it is going into overdrive or not. Thanks in advance for any suggestions!

 

[MrFleming007]

Ttt...

Ok, overdrive was dead, so I replaced the vss. Overdrive is back and the tranny seems to shift smoother. No change to the speedometer or trip odometer. Cruise is still dead too. We have a new multiswitch and brake switch that are confirmed to be working. Also took a multimeter to the cruise servo connection on the firewall and confirmed that each wire seems to be doing what it should .We also took a working servo off another truck and tried swapping that in- no go. What else could be causing these issues?

 

[MrFleming007]

Just to follow up on this, we picked up a used junkyard cluster for $10.00. Swapped the original odometer over and in the process discovered that the trip odometer in both the original and junkyard clusters had a broken plastic drive gear. I epoxied the gear back together, let it dry overnight and re-installed it. The trip odometer now works again!

And not sure what the problem was with the original speedometer, but it now reads within .5 mph of gps speed. Might have had a lazy servo in the old cluster.

So.... only issue left now is the cruise control.

 

[SunlitComet]

If fuse #6 CRUISE 10 Amp is good then most likely your stop light switch on brake pedal is broken.

 

[Gzes]

sounds like a big problem. i didnt know the 92-94 k5 could have cruise. mine doesnt have it. can u take a pic n show me?

 

[MrFleming007]

No #6 fuse in the 92-94 K1500 Blazers or 88-94 Trucks. From what I can find on LS1truck and fullsizechevy the cruise runs off the same fuse as the gauges in these years. Gauges run fine. Brake switch is working great and I've confirmed voltage off both connectors via multimeter. I'm starting to wonder if something in the DRAC module has gone out and may try this fix from LS1 truck...

http://www.ls1truck.com/forums/lsx-truck-conversions/25273-1993-obs-speedometer-cruise-control-wiring.html

I like a challenge, but this is getting ridiculous, lol!

 

[SunlitComet]

Here is what I got in diagrams:


Electrical Diagrams
Diagrams

Notes

Cruise Control Gasoline Engines (Part 1 Of 2)

Notes

Cruise Control Gasoline Engines (Part 2 Of 2)

 

[MrFleming007]

Here is what I got in diagrams:

Thanks, but its not showing up for me. I'm getting a Ford Door sticker diagram, and a exploded view of a rear end gear assembly, lol

 

[SunlitComet]

You took to long to look at your post. It has been refreshed above.

 

[MrFleming007]

Awesome, thanks! I'll take a look and get back to you!

 

[MrFleming007]

OK, with the help from the wiring diagram and another forum, I tested all the wiring for the cruise control yesterday. Biggest difference I noticed from the wiring diagram is that we have no white wire going to pin G on the cruise servo. It looks like this wire was never present on the 92-94 models? All other wires give the correct voltage ratings at the correct times with the exception of the vss signal wire.

This wire starts off at .04 volts at idle and increases to a max of 2.79 volts at about 20 mph. Never gets any higher than this as speed increases. Out of curiousity, we stopped at the junk yard and picked up a couple additional VSSR/DRAC modules. After setting them all to the correct tire/ Axle ratio we tried swapping them in and taking it for a test drive. First replacement module gave the same vss wire readings as the original. The 2nd module started off at 5.05 volts at idle, then dropped to .07 volts as the vehicle started rolling. This one too, maxxed out at 2.79 volts at around 20 mph and never got any higher.

So..... where to go from here?

 

[MrFleming007]

Allright, here is where I'm at. I've tested all wires according to the diagrams and everything looks good, but still no cruise. Tried three different cruise modules, still no go. Replaced the DRAC module with another (programmed to to correct gears/ tire size) still no go. So I'm at a loss. Here are the wires that I'm dealing with and the voltages that I'm showing on them.

Cruise Module Connnector

Pin A- Gray Wire (Cruise on/Off); Shows 12v when IGN on and cruise switch is placed in "on" position, 0v when "Off"
Pin B- Dark Blue (S/C Signal); Shows 12v as long as button at end of cruise lever is pressed, 0v otherwise
Pin C- Dark Green (R/A Signal); Shows 12v as long as lever on cruise stalk is pushed to far right position, 0v otherwise
Pin D- Brown (Cruise Release); Shows 12v when brake pedal is pushed, 0v otherwise
Pin E- Black w/ White stripe (Ground); Has good ground connection. Connects to Chassis Ground through orange three way connector on Convienence Center.
Pin F- Pink w/ Black stripe (IGN); Shows 12v when IGN is "on". Connects to 20a "Gauge" Fuse through Orange three way connector on Convienence Center.
Pin G- N/A, no wire
Pin H- N/A, no wire
Pin I- N/A, no wire
Pin J- White (PCM input); Shows 11.47v when IGN is on. Connects to PCM at connector C1/B10. Not sure what this wire actually does.
Pin K- Red w/ White Stripe. (VSS); Voltage varies with speed, starting at near 0v at idle, increases with speed. Has never shown above 4v. Connects to DRAV/VSSB module through Orange three way connector on Convienence Center, then to Pin 4 on DRAC/VSSB Module.

The cruise stalk in new and appears to be functioning properly. Have checked and cleaned all connectors between it, the PCM and cruise module and all are getting good continuity. The VSS is new and appears to be functioning correct. I can only at this point assume that the DRAC/VSSB module is functioning correctly as the RWAL system is working, and the speedometer is working and showing within .5 mph of GPS speed. The voltage on the Speedometer wire and RWAL wire is the same as the voltage showing on the vss cruise wire. The only wire whos purpose I am not sure about is the White PCM wire...

The Cruise modules I have tried are as follows;

P/N 25140076. Module that came in truck.
P/N 25140906. Came from 1994 K1500 Blazer with working cruise control.
P/N 25074973. Came from 1989 K2500 Silverado with 5.7l and working cruise control. This Truck did not have the White PCM wire.


So, at this point, I'm looking for any ideas. Thanks in Advance everyone!

 

[MrFleming007]

Well to update this, on Friday we got a CEL. Checked the code and it was for the egr. Pulled the egr and it was full of carbon and not holding a vacuum. Figured while we were in there replacing the egr, we would rebuild the TBI and replace the PCV valve. Truck runs even better than before now and.... CRUISE WORKS! Not complaining about that, but whats the relation here? Could the pending egr code have prevented the cruise from engaging?

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[SunlitComet]

what was specific code?

 

[MrFleming007]

Code 32- egr failure

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[SunlitComet]

there is no relation to the cruise, not even power wire wise so that will remain a mystery for now. You had gotten the 32 code becuase your short term fuel trim fell outside a calirated window when the egr vacuum solenoid closed off vacuum supply to the egr valve itself which can be caused by clogged passages. My best guess at this time is that you may have disturb a ground wire when doing the egr work that may have had a dirty connection.