05 Magnum hemi speed sensor

jwandhistools · #1 09-28-2009, 12:30 AM

Got a bad speed sensor on my 05 Hemi Magnum.
I am told the sensor is inside the trans, and the dealer want a fortune to swap it out.
Short of pulling the trans, I can't see why they want so much.

Can anyone shed some light on this for me?
The symptom is, the speedometer does not work on this car.
The gauge was tested and is good.

Where exactly is the sensor and should this only be done by the dealer?

I have been wrenching for close to 30 years and probably can handle it myself if I can get a procedure.

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jwandhistools · #2 10-01-2009, 03:47 AM

Don't everybody jump in all at once now.....

JoeGs05MagnumRT · #3 10-10-2009, 05:46 AM

the 722.6 has two speed sensors. here is an accurate quote from MB forum:
http://www.benzworld.org/forums/w210...ml#post3647185
note, this thread was discussing limp mode due to speed sensor failure.

"722.6 Conductor Plate

The conductor plate is on top of the valve body and houses six solenoids and two sensors, a few other things. Common failures are the two speed sensors, which cannot be replaced separately so the entire conductor plate has to be replaced. This part has also received multiple updates so make sure you get the latest part.

When the speed sensors fail, the ETC does not know the input/output shaft speeds so it does not (know) what gear the transmission is in. If the failure is intermittent, then the ETC will go into “Mechanical-hydraulic” limp home mode. If the problem is more severe, then the ETC triggers the “electric” Limp Home mode.

Typical symptoms of speed sensor failure are erratic shifting or no shifting at all. The best diagnosis is to read the codes in the ETC using special scanners. If there are 012 (108) or 013 (109) codes, then the problems are likely the speed sensors.

If no special scanners are available, then at east read the codes using a generic OBD II scanner. Chances are the Check Engine Light (CEL) is on. If the codes are P0715 or P0720, again, the problems are likely due to the speed sensors. I said likely because the generic P0715 is mapped to several Mercedes codes. However, based on what has been seen, P0715 is a pretty reliable indicator of speed sensor failure.

Yours truly replaced the conductor plate on a 1997 E320 and you can find the instructions here.
P.S. "G-AMG" posted a combined Photo DIY- 722.6 Conductor Plate and Regulator Valve Spring R/R DIY."

jwandhistools · #4 10-11-2009, 02:16 PM

There are no OBDII codes at all, and the car drives normally.
All gauges except the speedometer/odometer work normally.
We put in a gauge cluster from another vehicle.
Same result.

master tech · #5 10-31-2009, 12:12 AM

joeGs05magnumRT is right, there are two input speed sensors in the transmission. But you have 4 output sensors, each one of them are tone wheels. They also share information with the ABS module. You'll need a scanner to read the ABS module. Also changing tire sizes will change the speedo too.

jwandhistools · #6 10-31-2009, 01:55 PM

The car is unmodified and runs normally.
No OBD codes, no ABS light.
Just a dead speedo.