Dead SPEEDO and ODO

If you don’t have luck figuring it out you can always install a sensor at the transfer case like the manuals have and tap the speed sensor wire at the ABS module to feed back to the speedo

post#290 in this thread:

https://www.tacomaworld.com/threads/building-the-beast.23170/page-15#post-470945

 

That's extremely helpful, thanks!!

I really would just like to delete the Skid ECU all together and this could do just that. I will see if I am lucky and still have that speed sensor port on my transfer case.

The post reads that after '05 Toyota may have made a change. Mine is an '06 but definitely worth looking into.

 

It should work on your truck, this 2011 I now have (auto trans) has had the speed sensor installed since the front and rear end were upgraded and totally swapped out and no longer has the abs.

 

So you have this mod on your 2011 truck? The sensor signal goes straight to the speedo, no signal conversion required?

I am running 33's. Any guess as to what size drive cog I might need? 30T or 32T or...?

 

The PO’s shop installed it I just know it’s there and I hadn’t traced the wires to see how exactly it was done but I assume they wired it similar to the thread I linked.

It looks like you’d have to tie the one sensor wire into the speed wire at the abs unit or wherever it ends up inside the truck. The other 2 are just power/ground by what that write up said.

As far as which cog, I do not know. I do know the one that’s in mine is 5 mph off with 37s.

 

Automatic Transmission:

The Skid Control ECM converts the many pulses received from the #1 ABS Sensor into a calculated 4 pulse signal to the combination meter.

The Skid Control ECM does monitor all four wheels so that it can control the many functions of the ABS Systems. It only uses the right rear #1 Sensor for speed calculation to be displayed on the speedometer.

 

Since it was already installed you may not know this answer, but does the transfer speed sensor send a signal directly to the speedometer on your setup, or is the ABS ECM still looped in?

 

I don’t know where they ran and tapped the signal wire specifically as I haven’t traced it. But I can tell you that the abs unit had been totally removed, so it had no role in the speedometer anymore. So the mechanical sensor is feeding all the info to the speedo.

There were 3 wires cut at the abs unit harness plug, one of which if I recall was the speed wire. I was messing with the system a couple weeks back and threw an abs unit from a wrecked taco in to have the dash lights shut off. They may have tapped the speedo wire somewhere in the dash or at the kick panel.

 

I can figure out where to send the signal... just wasn't sure if your setup was a direct link or not.

Thanks again for the assistance.

 

Instructions in the post linked above certainly make it sound like the vehicle speed sensor sends a signal directly to the combination meter and bypasses ABS.

 

The wiring diagram DM93 was good enough to share does seem to show a direct link from a MT transmission speed sensor to the speedometer.

 

The answer is that on the manual transmission it goes to the Combination Meter then the ECU.

The Automatic goes to the Skid Control ECM then the Combination Meter and then the ECU.

Note on Post # 17 quoted here:

This is the path Automatic:

Speed signal >>---- Skid Control ECU>>----------->>Combination Meter >>------------>>PCM

DESCRIPTION
Automatic Transaxle Models: Vehicles, which are equipped with ABS (Anti-lock Brake System), detect the vehicle speed using the skid control ECU and wheel speed sensor. The wheel speed sensor monitors the wheel rotation speed and sends a signal to the skid control ECU. The skid control ECU converts the wheel speed signal into a 4- pulse signal and transmits it to the ECM via the combination meter. The ECM determines the vehicle speed based on the frequency of the pulse signal.

This is the path Manual:

Speed signal >>---------->>Combination Meter >>------------>>PCM


Manual Transaxle Models: Vehicles, which are equipped with manual transaxle, detect the vehicle speed using the No. 1 vehicle speed sensor.

The No. 1 vehicle speed sensor transmits a 4-pulse signal for every revolution of the rotor shaft, which is rotated by the transaxle or transfer output shaft via the driven gear.

The 4-pulse signal is converted into a more precise rectangular waveform by the waveform shaping circuit inside the combination meter.

The signal is then transmitted to the ECM.

The ECM determines the vehicle speed based on the frequency of the pulse signal.

 

Correct me if I am wrong here Jimmyh.

But from what I gather, as long as you are getting the appropriate 4 pulse signal to the Red-Yellow wire / pin#6 of the combo meter, it should work.

What I can’t say is, that the pulse generated will be correct.
Evidently it should be, if you go by the link posted earlier?

 

Yes, that is correct. The Speedometer corrects the 4 pulses to a clean square wave signal for the ECU in both manual and automatic transmission models.

The issue with the automatic is that the ABS wheel speed sensor (Right Rear) has an lot more pulses that need to be correlated into the proper ratio for the speedometer ( 4 pulses per revolution like the manual gear driven sensor ). Then the speedometer does the same thing as a manual and generates a clean square wave signal for the ECU.

 

Finally got my SPEEDO and ODO working again. Only problem now is I am about 5 MPH off. But I am running 33" tires so that's close enough for now. But if anyone has cog swapping input I would be all ears. Current gear is marked 11 / 30.

Here is some info and how I made it work.

I picked up a transfer case speed sender off an old Tundra I found at the salvage yard. Sorry I don't have any specifics, but my guess is this sender is found on many Toyota models and even on Amazon. Keep in mind however that if you by a new stand alone speed sender you won't have the plug and will have to sort that out as well.

The sender:



As others have mentioned, even the AUTO transmission Tacomas that generally receive the speed signal from one of the ABS wheel sensors appear to have the transfer case port and worm gear required for the speed sensor to be installed.

Sensor port (back of transfer case at rear driveshaft):



Port cap removed with worm drive visible inside:



The port cap itself:



I simply removed the cap and inserted the speed sensor. It was a tight fit. So tight in fact I had to reduce the diameter of the speed sender by sanding slightly where it slips into the transfer case. Didn't take much and I probably could have forced it in, just wasn't sure if I could ever get it back out. O-ring groove remained untouched as to not effect the seal.

From there I went on to the wiring. The speed sender has a three prong plug that needs to be wired as follows:

Pin 1: 12V (switched is probably preferred)
Pin 2: Ground
Pin 3: SPEEDO signal

I ran three wires from the ABS module harness under the hood. I spliced into the following wires or pins:

Pin 1 to Pin 46 (LG wire)
Pin 2 to Pin 1 (W-B wire)
Pin 3 to Pin 18 (R-Y wire)

Overall very happy. Eliminated the ABS connection which was for me problematic and simplified the overall system greatly. For my needs at least.

Wiring diagram files just so you don't have to search the thread to find them.



Thanks everyone for their input and help!!

 

Nice. Thanks for the update.

 

Well done, I just got done doing my writeup on the P0500 code but looks like you got it all sorted except the speedo being a few MPH off.
I would imagine there would be different gears for the speed sensor as there are a couple different axle ratios available depending on the engine/transmission.

 

I went down the rabbit hole on which cog to go with a couple months back. The posts in the below link (particularly #503 and 510) may be of use and have some part numbers. My speedo is about 5mph too fast and I am going to swap to a different a cog at some point whenever I get around to pulling my sensor and seeing what cog I currently have.

https://www.tacomaworld.com/threads...d-and-adventures.484602/page-26#post-17243636

 

Thanks. I just need to figure if I need to go one or two teeth up or down to compensate.

 

Sorry to revive a dead thread. Do you happen to know (or know where I can find) the correlation for the squarewave for the tachometer signal on a 2.7L? For example: x Engine RPM = y 5V Pulses/sec.

Long story short, I am trying to manualize the transmission and use an engine speed lockout for downshifts.