A friend's 2000 F250 SD 5.4L is throwing code C1229 and the ABS light, indicating an issue with the rear diff speed sensor. He has already replaced it twice. It currently has an O'Reilly part in there.

From AllData I have downloaded the pinpoint test G for MY 2000 and I am now very confused. It says to measure the resistance of the sensor and if it is less than 10,000 then replace the sensor. I measured 1,900 Ohms. We then went to AutoZone gave them the vehicle details and they sold us Duralast SU2175. This also measures at 1,900 Ohms.

This makes me think that there is a mismatch between Ford and third-party sensors. However I am failing to find the part number for the Motorcraft sensor. Can anyone help me find it? AllData does not show a part number.

Update: Looks like it is F85Z-2L373-AC but I am still unsure of the resistance values issue.

Thanks!

 

The article you posted says to measure each pin to ground, not to each other, this is looking for a short inside the sensor to the diff. Also it’s been known that aftermarket sensors are junk and to stick with Motorcraft sensor if you can.

 

Yes, you are right, however the next step in the testing is to measure more than 10,000 ohms between pins 9 and 21 on the breakout box, which means pins 9 and 21 on the ABS connector. I measure the same - 1,900 Ohms.

 

Can you post the entire test sequence, I don’t have access to all data but it looks like your performing test J or K if what I have matches up.

your sensor should read between 800-2500 ohms
with the sensor unplugged,

with the sensor unplugged and between each sensor leg to ground should be higher then 10k ohms

*****All test below are testing the harness, not the module or sensor*****

with the sensor unplugged and the ABS module unplugged, measuring pin 9 to ground should be higher then 10k ohms

with sensor unplugged and the ABS module unplugged, measuring pin 21 to ground should be higher then 10k ohms

with sensor unplugged and the ABS module unplugged, measuring between pin 9 and pin 21 should be higher then 10k ohms

with the sensor plugged IN and the ABS module unplugged, measuring between pin 9 and pin 21
should read between 800-2500 ohms

if all these tests pass then there is no wiring or open/shorted sensor fault and you need to start checking other things.

 

Thanks - that is a good point about the pins 9-21 test being with the sensor disconnected. Attached is the entire pinpoint test G for code C1229. No mention of 800-2500 ohms. I will put the old sensor back in and continue with the pinpoint test.

Meanwhile I took your advice and have ordered a Motorcraft sensor from Rockauto as it is discontinued/obsolete at Ford Dealerships.

The testing of sensor to ground really means testing each pin to the the metal lined bolt hole on the sensor, right?

Thanks for your help with this.

 

Not the metal sleeve on the sensor, that’s there just so the bolt doesn’t crush the plastic sensor, the purpose of testing each sensor pin to ground(diff housing not frame) is to determine if the housing of the sensor has cracked and is shorting the sensor internals to the diff housing.

Test G6 is looking for a short between the two wires that go to the diff sensor, they don’t say to unplug the sensor, they just assume the person testing will know this.

The tests I posted above will check if pin 9 wire is shorted to ground, pin 21 wire is shorted to ground, pin 9 wire and pin 21 wire shorted to each other and if those all pass, you plug in the sensor and measure pin 9 wire and pin 21 you should read your sensor ohms which will indicate that the wires aren’t broken either.

The sensor resistance of 800-2500ohms is in another test section.

 

Thanks. I jiggled the sensor connector and the resistance at the ABS connector went crazy. Removed the connector and it has bad/amateur butt connections on an after market hacked-up connector.

Got a Standard Parts S699 as a replacement and, of course, the connector does not go onto the sensor all the way.

Now thinking of going to a junkyard and pulling a factory connector...