No speedo

Taker730444 · Aug 13, 2018

Have an issue with no Speedo. I have a code c1145 for front right wheel speed sensor. I put the gauge cluster into HEC test mode to check to see if I was registering speed and it is not It just stays at 0. The HEC test mode is also displaying code d043 meaning there's no signal from the traction control. Any ideas could these be related am I needing to replace the wheel speed sensor to make the speedo work or the VSS on the transmission?

wmburns · Aug 13, 2018

I give up. What Model year Mustang are we dealing with? The trouble shooting steps are different dealing with 1996-1998 VSS sensor equipped car verses 1999-2004 OSS equipped mode.

VSS 1996-1998 The VSS signal goes to BOTH the PCM and the cluster.
OSS 1999-2004 The OSS signal goes ONLY to the PCM. The PCM then "tells" the cluster what to display via SCP network commands.

FWIIW, IF there's no speedometer THEN the bad wheel speed sensor is NOT the cause.

It will help trouble shooting to know what the PCM "thinks" the car's speed is. This is best done with an ODB2 scanner. I'm sure that you can see that the trouble shooting is slightly different depending upon the model year and the symptoms.

For the 1999-2004 model years knowing what the PCM's state of speed will either rule in or out a possible OSS sensor problem.

IF the PCM has the correct speed and there's no speedometer then more trouble shooting of the SCP network or cluster is needed.

Taker730444 · Aug 13, 2018

Sorry I forgot to put in 99 Mustang GT

wmburns · Aug 13, 2018

Taker730444 said:
Sorry I forgot to put in 99 Mustang GT

With this being an OSS car it's even more important to the trouble shooting process to know what the PCM's speed status is. This will give focus to the trouble shooting by either ruling in or out the transmission OSS sensor as the possible trouble source.

FWIIW, here's some direction that may help. The 4R70W is a PCM controlled transmission. IF this car is an automatic AND the transmission shifts OK, then it's reasonable to assume that the PCM is getting a solid OSS signal. Again if true your problem lies between the PCM and cluster. Go back to the cluster diagnostic mode. Does the speed display in the diagnostic mode? If so, this proves the PCM to cluster communication is working.

Should it turn out that your problem is in the cluster, check out this thread on Cluster PC foil trace repair.
https://www.allfordmustangs.com/forums/v6-tech/304608-my-odometer-goes-off.html#2657361

Taker730444 · Aug 15, 2018

Some other information I forgot to include sorry LOL. Mine's of manual transmission.

Now I'm having an issue PCM is not registering speed so I'm assuming it's the speed sensor needing to be replaced. Now here's my dilemma AutoZone and O'Reilly's both list for a 1999 manual T45 transmission only the Gear Drive sensor. Or an automatic transmission sensor which looks similar to The One I Got. I know it's not either of these. when I Google it the sensor that comes up has a single o'ring unlike the automatic transmission sensor which has two o rings.

wmburns · Aug 15, 2018

FWIIW, an OSS sensor rarely goes bad. But why guess? Test!

The OSS sensor generates it's own output AC signal. Disconnect the OSS sensor and put an Volt-Ohm meter (VOM) on the output of the OSS sensor. With the rear wells up on axle stands put the car into gear. Measure the output of the OSS sensor. The AC voltage should vary as the speed is increased.

If you have an advanced VOM that can measure frequency that will give a more direct speed output.

The other test is to remove the OSS sensor and verify that the tip of the sensor is still magnetic.

It could help others to post a picture of the sensor.

If this were my car I would also do a through review of the wiring harness. Look for evidence of physical damage, rodent activity, or water damage. If asking for an handicap this is the most likely problem source (wiring).

Here's some information on an alternate way to test for a "reasonable" speed sensor output. The video calls the sensor a VSS but it's actually a no contact OSS style sensor. The take away should be how an advanced meter can show that the sensor is working and responding to speed changes.

EP. 11 - Autel AL539 B - Graphing The Vehicle Speed Sensor (VSS)

View: https://www.youtube.com/watch?v=GTe9TfofBhg

Taker730444 · Aug 15, 2018

Taker730444 · Aug 15, 2018

Found the problem with speed sensor.... started searching further up the harness for traps are in the transmission in the engine bay and found the mouse to Tamar's which so happened to be the speed sensor. Problem fixed

wmburns · Aug 16, 2018

Taker730444 said:
Found the problem with speed sensor.... started searching further up the harness for traps are in the transmission in the engine bay and found the mouse to Tamar's which so happened to be the speed sensor. Problem fixed

Did you find rodent damage? How did the repair go?

Was the information received from the forums helpful? Would you have been able to find the problem on your own?

Taker730444 · Aug 17, 2018

Rodent damage was right where the output speed sensor wiring comes out of the main harness. I had to use razor blade cut the tape away from the area to be able to pull excess wire from the main harness to give enough length for a repair. Used a small hand torch and solder with heat shrink. It was a tight space to work in for the torch but doable. Thanks to the help and diagnostic tips I was able to find this issue.

Now on to the next problem with the speedo pretty sure I already know what the issue is just want to double-check I'm on the right track. When I'm doing about 65 on the interstate the speedometer is reading 80mph. The Gauge cluster is out of a V6 and I imagine that's part of the problem. It also has 4:10 gears in it. But I'm guessing changing the cluster back to a gt cluster will make a big difference then after that having the computer calibrated to the 4:10 gears should level it out. Also what if I was to buy new gauge faces for a GT and just put it over the V6 ones would that work? Am I right or should I be looking elsewhere with that big of a speed difference.

wmburns · Aug 17, 2018

To answer your question we need to go back to HOW I explained the OSS speed sensor works on the 1999-2004 model year. To find out IF the correct adjustment for gears has been done we need to know what the PCM "thinks" the car's speed is. Remember that the PCM "tells" the cluster what speed to display.

IF the PCM speed is correct the next step is to compare the amount that the cluster is off. IF the over lay is responsible for the error the difference should be a ratio between the top speeds of the two over lays. IE, 150/120=1.25.

I wish more people would update their threads with this information. I see way too many threads that start out with wanting to load up the "parts cannon" to solve problems. IMO it happens all to oven that people give up when the hard work of tracking down a difficult wiring harness fault. Good work!

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