Hey gang been a while .... so busy lately....

Started today .... I've had ABS light for a while .... finally got around to changing both wheel hubs out a few weeks back .... no difference. Rear sensor seems clean.

today speedo stopped ......

How to track down ;)

I did it from reverse.

OHM reading from the sensor - basically disconnect, set on OHM , complete the circuit - got a reading.

When my mechanic checked mine, he said the front driver's sensor was bad. I replaced it, light still on. Then I replaced the passenger's, then rear, light still. Checked connections, wiring, all good. Then a different mechanic ran his $10,000 snap on reader for free, the ABS module kept cycling and he said it was the ABS control module. I get it replaced and vin coded this Friday, I'll report my findings. Also, when I replaced my rear diff sensor with an O-Reilly's unit, it was defective and my speedo would come and go intermittently. Then I ordered the OE part from Rock Auto, and the speedo is all good. As 98whitelighting said, it may or may not have something to do with the p-pump conversion. Are there any other symptoms other than loss of speedo and abs/light on? When I replaced the front hub on my 2003 hemi, there was too much grease in the unit the sensor would think the brakes are locking up and my ABS would go off. I had to take the sensor out and pick some of the grease off the teeth and it cleared up. 

Only real concern is odometer and speedo. Would have thought it was a wiring or fuse issue except it magically started working again about half way home ......today

Time to use some dielectric grease on connectors...

Really .... couldn't be that simple right ?

You never know...

Dead this morning

There is a lose connection in the rear ABS sensor for it to work for a short time. Check again...

Reseated sensor and harness by wheel well .... used dielectric also

No change

Edited April 2, 201510 yr by JOHNFAK

Ohm reading wire end to wire end. Check to see if it's in the range of 0-5 ohms. (Without the sensor). Might be the wire is corroded or something. For it to work for a short span and quit is a loose connection or broken wire. With it dead right now the sensor should show as a open circuit or excessive high ohm reading .

 

Any lights or error codes?

Yeah I guess I'm looking for how to approach now.

 

Will OHM out the harness from sensor back to wheel well. And see how I can ohm it out from wheel well back to cluster and update with readings.

Guess Im wondering also on a couple of things

 

1) How to check that the connection to back of cluster is good - I know the cluster itself is fine. Pull the harness from wheel well and ohm out the harness connectios goign back to engine bay from there ?

2) How to know its not a tone/ring/gear pickup issue in rear diff ?

3) How to confirm that OSS sensor in transmission has no bearing on this - reading mixed views based on differnt year trucks and peoples understanding of the speedo

 

Lights are check engine[ppump]/ ABS and brake light.

Codes are missing injection pump, overboost (twin turbo), grid heaters ........

Edited April 2, 201510 yr by JOHNFAK

So ........ ohm readings

 

1) Unplug sensor and bridge the sensor pins - 1.9k ohm

2) Measure the ohm by bridging the female connector of harness plus - 23k ohm

3) Pull harness plug on drivers wheel well. Reads 1.9kohm going back to rear...... 23kohm going up to PDC.

 

Not sure what all that means ........ obviously measuring resistance but basically I take it if it has a reading (NOT OL) then its ok.

 

 

**SIDE NOTE** - dont know why - but the last 2 times I've driven with it dead ..... and I speed up over 60mph ...... it engages ..... and stays engaed until I turn the key off ...... then we go back to DOA. Could be just a coicidence.

 

 

*shrug* 

 

Deal told me couldn't put it on a scanner until 14th April and would be $120 for DRB scan. ......... nuts. Other scanners pulled the codes listed above only.

That wire is shot.

 

Even with 18 AWG at 1,000 feet long is only 6 ohms.

https://www.cirris.com/learning-center/calculators/133-wire-resistance-calculator-table

 

The bad part is that lead is twisted pair.

 

 

So this tells me the ABS/Brake light is on because the ABS computer can't see a good signal from the sensor. ABS system is totally separated from the ECM/PCM but rides on the CCD Network. As for the speedometer signal its easy as long as all the other gauges are working the CCD network is functional. Speed signal is embedded in the CCD network and travels with the other signals (oil pressure, volts, temperature, etc.)

Could I be measuring it wrong ...... its just on autodetect on my multimeter.

Don't understand why it would read 23k ohm one way ...... and 1.9kohm the other .......same wire

 

ok just went and did it again.

Assuming Im doing it ok (basically bridging both wires rather than grounding and connecting to 1 wire at a time).

I get 1.9k OHM going from the truck fender back to the rear diff. I get 23 going back from driver side wheel well harness back to cab.

So if theres a bad connection/wire I guess its somwhere in the harness from the wheel well going back up which splits into 3

 

1 Run to Cluster

1 Run to PDC

1 Run to ABS module.

 

 

So how do I track this down further --- to isolate as a faulty wire rather than bad ABS module, or cluster connection or PDC connection. 

 

If I do need a new wire then ??? New harness ?? Where from ???

 

thx

Edited April 3, 201510 yr by JOHNFAK

Better connection with the contacts perhaps. Either way both measurements are high.

Maybe using a long single straind of wire and do each lead separate and see what happens? I wonder if the twisted pair is adding a amount of resistance being your running both leads.

Maybe using a long single straind of wire and do each lead separate and see what happens? I wonder if the twisted pair is adding a amount of resistance being your running both leads.

Lost me.

 

Actually it seems the resistance is comming from the harness back to the cab from the wheel well drivers side. Drievrs side back to rear of truck is ok.

That harness splits into 3 ....... ABS, CLUSTER and PDC.

 

So how to chase the wire issue or a bad connection - eg PDS is hardwired right ??

Any discontinuity will be between the areas of high resistance. Basically, we need to find the break and replace that section or fix the discontinuity.  

 

you should be able to find the fault/break or area of high resistance with your multimeter.   If you run your leads through each combination of the split, you should be able to isolate where the leak is.  One lead should be on the sensor end, and then put the other into each individual leg of the split... if they all ohm the same, then the leak should be in the sensor end of the wire.  You can also ohm between each leg of the split.  

I would suspect a break in the wire itself or that a wire has become unhooked in the plug itself.  You might be able to disassemble the plug and try fixing it or testing the resistance of the wire alone.  

 

What mike is taking about is to take a set of wires and bypass the factory wiring and see if it works, to test the theory that the wire is bad.  

sure .... but its the physical ohm of the next step of harness I mean. Not sure how to do it.

Basically if I ohm from the drivers side wheel well back up to harness towards cab I get 23k ohm. So if I follow that harness back to cab - it basically routes into the MAIN harness at a 3 way junction right by steering shaft..

 

So

1 junction goes into Cluster - not sure how to OHM that out unless I pull the cluster and then unsure what pins. Even if its ohms out bad - then what ?

1 Junction goes to ABS module. This would be easiest as its a plug - but which PINS and if it ohms out bad - then what ?

1 Junction goes into hardwired to bottom of PDC -  not sure what I can do here at all.

 

make sense ?

I like the idea of running a wire to test that its a connection/wiring issue - but from where and to where ? And if it works - then ??

 

*shrug*

Good point. doesn't the articles have a good color coded wiring diagram?