No Speedo

E

e10pvmt

New member
So i have no speedometer/ODO. Only code being thrown is the P0500 speed sensor A.....a lil background

Ive built and entirely new chassis so the brake system is entirely new with wilwood calipers and a GM hydroboost unit. No ABS sensors and i have removed the VSC, ABS, and Traction control computers since i don't need them. Yaw rate sensor as well. All the other gauges work fine. Temp, fuel, and tach.

Now my question is. Does the speed signal route through the VSC computer thats under the dash? I have checked the tailshaft sensor and it appears to be fine and sends voltage when a magnet is waved past it while hooked to a multimeter. Before tearing my truck apart i unplugged all the wheels sensors and the speedo worked fine. I can't see on the schematics where the speed signal is routed through the VSC or Yaw rate sensor
 
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For the automatic transmission equipped vehicles, the wheel speed sensors input wheel speed to the skid control unit for the ABS. The skid control unit gets a reference voltage from the speedometer in the combination meter (instrument cluster) and the skid control ECU pulses the signal to ground for the speedometer and odometer to operate. The combination meter then sends the VSS signal to the ECM.



Hope that helps!
This is also my first post here on t4r. I own a 2003 limited v8 myself.
 
if thats the case then how come the speedo worked fine before I took everything apart when I unplugged all the abs sensors at all 4 wheels? Besides the sensors ,the master cylinder and everything that goes with it is non existent anymore. Is there anyway to bypass this and have the speedo work?
 
Hmm. Well if you had it all unplugged and it was still functioning, it was probably running off of the sensor in the transfer case. Is the ODO not displaying anything or just not counting? Do you have cruise control and is it operating?
 
I don't have cruise because I removed the controls. The OFO is displaying just not counting. Niether is the MPG countig....it will display miles to empty when I disconnect the battery but then over time counts to zero
 
have you tried re-installling the skid control ecu for the sole purpose of translating the signal from the VSS? I do not know of a way to bypass it, as it basically takes the language the sensor speaks and translates it to the language that the cluster understands.

Due to the fact that the only difference in the system from when you took just the wheel speed sensors off and now is that your modules are not present, one can assume that your vehicle speed system was operating via the sensor in the tranfer case and the signal was routed/translated through the module. try power/grounding the module and routing just the speed signal through it.
 
I just reinstalled the skid control ecu...so cross my fingers that works...thanks for your help. I'll let you know what happens. I will give it a couple days of driving...I know it may not be immediate
 
As was mentioned, vehicle speed is determined via wheel speed sensors and then translated through the Skid Control ECU into a VSS output to the Instrument cluster (which is in and of itself a module) and then it outputs it a speed reading. Not entirely sure why the speedometer worked when you had all 4 wheel speed sensor disconnected as in the diagrams it didn't seem to mention the tailshaft sensor being used by the Skid Control ECU from what I remember.

Out of curiosity why did you switch to a GM Hydraulic Brake Accumulator?
 
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Im at a loss for why it worked as well...cleared the code and after one trip around the block, nothing. I switched to a gm hydroboost because I built a full chassis with a custom ifs and a supra irs...complete air ride setup and all wilwood brakes...the oemaster cylinder unit interfered with my wheels and the stock brakes obviously wouldn't work with the setup I have....any idea what the tacomas are using? They have a vaccum boost but does there speed come from the wheel sensors?
 
e10pvmt said:
Im at a loss for why it worked as well...cleared the code and after one trip around the block, nothing. I switched to a gm hydroboost because I built a full chassis with a custom ifs and a supra irs...complete air ride setup and all wilwood brakes...the oemaster cylinder unit interfered with my wheels and the stock brakes obviously wouldn't work with the setup I have....any idea what the tacomas are using? They have a vaccum boost but does there speed come from the wheel sensors?
Click to expand...

The '05-'09 Tacomas use a traditional vacuum boosted braking system, but they still have an ABS module and Solenoid pack (separate from the MC) that still uses all 4 wheel speed sensors ('10-'15 models use the hydraulic master unit the 4Runners, FJs, ect. use.) As far as I know, Toyota has been doing their vehicle speed this way for about 10-15 years now.
 
ok so CEL is back on and no speedo after a couple hundred miles this weekend. I noticed when i plugged in the skid control ECU under the dash the alarm was screaming and the only thing i could was unplug the alarm connection. I've read about a zero point calibration and for the Yaw sensor and i noticed it mentioned in the FSM when working on the instrument cluster. Could any of these be a potential fix? And why would the alarm be going off if it isn't detecting any input from the wheels?

After doing a little digging into what the solid axle swap guys are doing i found some fixes and maybe some clues as to my issue. The below link is the diagnostic flow chart for the 4runner. It says i may be getting a signal from SP2 but not SP1. Any idea which one is which? i know there are 2 sensors on the trans. One on the tail shaft and one up near the bell housing. I also had the guy on the forums here swap the LEDs in my cluster. Could something have been damaged in that process to mess with the voltage regulator on the back of the cluster? While searching google i found someone with this issue so i will have to meter that connection.

http://www.ezdries.net/Vidpics/4Runner%20Repair%20Manual/2003/2003%20Toyota%204Runner%20Repair%20Manual/Diagnostics/SFI%20System%20(1GR-FE)/cip0500.pdf

As a possible fix i noticed the 4wd guys using a worm gear speed sensor and tapping into the skid control edu but i don't think that will work for me since of course i have no transfer case. However i did notice some people using a gps interface or a dakota digital electronic speedo interface and tapping into the wires feeding the signal to the cluster.
 
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Ok so it works now....nothing could be done without some sort of customizing....the speedo reads off the rear wheels sensors which i no longer have.....I chose to use the Dakota Digital SGI-5.....tapped the signal off of the tail shaft sensor and then routed through the box and into the speed output on the VSC ECU harness....the box allows for infinite adjustment....speedo now reads exact according to a gps....no CEL anymore and my ODO, trip, distance to empty, and mpg displays all work now......this will work for anyone who for any reason removed the rear wheels speed sensors or needs to recalibrate there speedo.....so SAS, new gears, larger tires, etc
 
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