ABS, ESP and spinning wheel lights – no signal from rear wheel sensor

2005 158” 2500 cargo van

Background: I decided to tackle my intermittent ESP lights. Pulled codes and got 53CF: return pump, which is a bad power or ground to the ABS module / pump. Disassembled the connector as pin 23 (switched power source) looked to have poor spring contact. (I would recommend that no one ever try to disassemble this connector as, due to the weatherproof seals, it was nearly impossible to get back together.) Massaged socket on pin 23 and reassembled the connector. Turned ignition on and checked for codes – had bad RIGHT rear wheel sensor code. Went to check resistance and saw that the pins for the right rear wheel speed sensor went back into the adjacent (wrong) slot in the connector. Moved pins back to correct slots and verified 1.8+/.1 kOhms on all 4 wheel speed sensors. No codes with ignition on.

My current problem: After performing work described above, I drove about 100 yards and all three lights come on. Code is bad LEFT rear wheel speed sensor. Live data shows LR speed sensor constant at 0 mph all the time. Re verified 1.9 kOhms on LR sensor pins at ABS module (per Xentry pin out, as pin location in 2006 service manual are different). Put an oscope on LR sensor pins at ABS sensor, jacked up LR and spun wheel – signal is just noise. So I decided to prove oscope settings and jacked up RR (working) wheel and put oscope on RR pins at ABS connector. Spun wheel by hand and no signal on oscope. I recall the service manual (or somewhere) says that when testing speed sensors the wheel needs to go 1 rev / sec, so I got an electric drill to spin the wheel faster – still no signal. Decided to look at speed on scan tool so reattached connector and turned ignition on, spun wheel with drill and still 0 for wheel speed. Started engine with transmission in neutral and spun rear wheel with drill – still 0. Contemplated putting car in gear to spin wheel faster, but decided I needed a break before attempting that.

Convinced myself I could put the car in gear with one wheel off the ground an put the car in drive and not kill myself, so that is what I did. Got the revs up to about 1200 rpm (the limit of my bravery) in 1st with RR wheel in the air and scan tool and speedometer still reports 0 at RR wheel speed sensor; could see the RR wheel spinning in the rear view mirror. Gave up on testing wheel speed sensor while stationary. Went for test drive and 3 wheel speed sensors (including RR, which is the one I was attempting to read with the car stationary) give good data and LR still gives 0 all the time. Just to be clear, the reason I was trying to get RIGHT rear speed data was to prove my test setup, which I was never able to successfully do - my problem is the LEFT rear.

Decided to pull LR speed sensor and clean it and adjust gap. Cleaned sensor and set gap to the thickness of a sheet of paper and went for a test drive. LR still reads 0. Other 3 still give good data.

My questions: Does anyone know a good way to test a wheel speed sensor? I remember reading somewhere that passing a magnet near it produces some kind of signal. Can anyone verify that? Anyone successfully measured the signal on an oscope? I don’t think I have a wiring problem as I get the same resistance on the LR sensor as all the others. Any ideas what to do next? Replacing the sensor is my next step, but I’m not convinced it is bad and I’d like to confirm it bad before soldering wires while lying under the car.

Thanks!

Any time you pass a piece of ferromagnetic metal across the sensor, it will produce a signal. It doesn't need to be a magnet.

^^^ key word being “pass”.
In use the sensor generates a pulse in response to the CHANGE in the magnetic field as the ferromagnetic (steel) teeth of the tone ring cross the sensor face. This is the typical system (though the animation shows the field lines incorrectly, extending them into the passing air gap rather than into the teeth):
https://www.youtube.com/watch?v=YeXlmdlXp2s

But do our sensors have a permanent core magnet?
(Edit: MWD says YES) or is there a DC current sent from the CAB to generate the required magnetic field? If the latter, it could explain why your test rig is not picking up a signal while the CAB does.

-dave

The core is a weak magnet They will produce ac voltage even unconnected. As mentioned its between 2-6VAC from my testing.

Midwestdrifter said:

... As mentioned its between 2-6VAC from my testing.

Click to expand...

I just skimmed the thread, so maybe mentioned already...

I assume that is when using a digital voltmeter. An older style analog meter might load down that fairly weak signal. FWIW.

It is possible that the rear tone ring segments got distorted during work and could be further away than some. In that case the signal could be intermittent, or might not even register depending upon the instrument used for testing.

vic

I found some time to get back to troubleshooting this. I decided to cut both wheel speed sensor wires near the rear axle (they had crimp connectors there already) and swap the wires. In both conditions (RR sensor connected to RR harness & LR sensor to LR harness OR swapped so that LR sensor connected to RR harness & RR sensor to LR harness) I get 0 speed in the live data when driving (1.88km/hr actually - which is what my icarsoft reports when stopped) at the LEFT REAR wheel speed sensor.

So I have conclusively proved that my LR sensor is good. There are 2 options: bad LR sensor wiring between the ESP module and the rear axle or bad ESP module. Since I get the expected 1.9kohms at the ESP module for the LR sensor (see post quoted below), I suspect I have a bad ESP module. Any thoughts on this? If I do have a bad ESP module, where can I get one? - I don't want to touch the brake lines as I don't want to bleed everything, so I just want to replace the electrical portion.

99sport said:

2005 158” 2500 cargo van

Background: I decided to tackle my intermittent ESP lights. Pulled codes and got 53CF: return pump, which is a bad power or ground to the ABS module / pump. Disassembled the connector as pin 23 (switched power source) looked to have poor spring contact. (I would recommend that no one ever try to disassemble this connector as, due to the weatherproof seals, it was nearly impossible to get back together.) Massaged socket on pin 23 and reassembled the connector. Turned ignition on and checked for codes – had bad RIGHT rear wheel sensor code. Went to check resistance and saw that the pins for the right rear wheel speed sensor went back into the adjacent (wrong) slot in the connector. Moved pins back to correct slots and verified 1.8+/.1 kOhms on all 4 wheel speed sensors. No codes with ignition on.

My current problem: After performing work described above, I drove about 100 yards and all three lights come on. Code is bad LEFT rear wheel speed sensor. Live data shows LR speed sensor constant at 0 mph all the time. Re verified 1.9 kOhms on LR sensor pins at ABS module (per Xentry pin out, as pin location in 2006 service manual are different). Put an oscope on LR sensor pins at ABS sensor, jacked up LR and spun wheel – signal is just noise. So I decided to prove oscope settings and jacked up RR (working) wheel and put oscope on RR pins at ABS connector. Spun wheel by hand and no signal on oscope. I recall the service manual (or somewhere) says that when testing speed sensors the wheel needs to go 1 rev / sec, so I got an electric drill to spin the wheel faster – still no signal. Decided to look at speed on scan tool so reattached connector and turned ignition on, spun wheel with drill and still 0 for wheel speed. Started engine with transmission in neutral and spun rear wheel with drill – still 0. Contemplated putting car in gear to spin wheel faster, but decided I needed a break before attempting that.

Convinced myself I could put the car in gear with one wheel off the ground an put the car in drive and not kill myself, so that is what I did. Got the revs up to about 1200 rpm (the limit of my bravery) in 1st with RR wheel in the air and scan tool and speedometer still reports 0 at RR wheel speed sensor; could see the RR wheel spinning in the rear view mirror. Gave up on testing wheel speed sensor while stationary. Went for test drive and 3 wheel speed sensors (including RR, which is the one I was attempting to read with the car stationary) give good data and LR still gives 0 all the time. Just to be clear, the reason I was trying to get RIGHT rear speed data was to prove my test setup, which I was never able to successfully do - my problem is the LEFT rear.

Decided to pull LR speed sensor and clean it and adjust gap. Cleaned sensor and set gap to the thickness of a sheet of paper and went for a test drive. LR still reads 0. Other 3 still give good data.

My questions: Does anyone know a good way to test a wheel speed sensor? I remember reading somewhere that passing a magnet near it produces some kind of signal. Can anyone verify that? Anyone successfully measured the signal on an oscope? I don’t think I have a wiring problem as I get the same resistance on the LR sensor as all the others. Any ideas what to do next? Replacing the sensor is my next step, but I’m not convinced it is bad and I’d like to confirm it bad before soldering wires while lying under the car.

Thanks!

Click to expand...

You can leave the valve body, and just replace the electric module. You might slightly tweak the pins at the module, just in case it's bad contact.

I finally found some time today to get back to this project. My left and right wheel speed sensor wires were switched at the back axle, and that caused me a great deal of confusion when I tried to troubleshoot. After switching them to the correct sides things started to make sense.

Both my rear wheel sensors are good - I get sinewaves from each on the scope even at very low speeds. Both sensors have 1.8Koms resistance. My original problem was the ESP sensor losing power, which I believe was caused by an intermittently functioning ESP module. I replaced it with a junkyard unit - the replacement sensor has not disappeared from the network like the old one did occasionally.

I still have one problem, and I created it. When I was troubleshooting, I removed all the pins from the connector at the ESP module to check the wiring (the swapped rear speed sensors gave symptoms that appeared to be due to bad wiring). When I put the connector back together, I had two pins in the wrong slots - this immediately set the appropriate codes and I repinned the connector to the wiring diagram in the Xentry tool and that fixed the codes.

Here is my current problem: My left rear wheel speed sensor shows 1.8Kohms and generates the appropriate voltage wave form with the ESP module connector disconnected. As soon as I seat the connector, the resistance drops to 0ohms and I get no waveform on the circuit when spinning the wheel. The mating pins in the ESP module show 6Megaohms across those pins with the connector removed, so I dont think the problem is in the module, but rather is a physical short within the connector caused by seating the connector. As I now have two ESP modules, I tested both and I get the same short on the line with either module when I fully seat the connector. I will disassemble the connector tomorrow in the daylight, but I thought I'd see if anyone has any ideas on what might cause this or if anyone has ever seen a similar problem with a connector.

Thanks.

99sport said:

... As I now have two ESP modules, I tested both and I get the same short on the line with either module when I fully seat the connector. I will disassemble the connector tomorrow in the daylight, but I thought I'd see if anyone has any ideas on what might cause this or if anyone has ever seen a similar problem with a connector.

Thanks.

Click to expand...

I have nothing specific.

Is the area of the short where the wheel sensors were mixed up? If yes, your problem may be related to some slight difference in the mating of the connectors. The connector may have been damaged if forced into the wrong position.

Great work to find what you did. Keep us updated.

vic

Any chance a stray wire strand is shorting somewhere? Is it possible the harness is damaged under the wrapping?

Also note that the wheel speed sensors are sheathed for most of the run. A few inches before the ABS module connector, they are spliced with the colored wire which runs to the plug/connector. At least some vans are this way. Not sure about all models.

Its possible the splices are damaged? Might be worth unwrapping part of the harness for 5-6" to have a look.

I'm trying to remember the wiring diagram, I got into it with my rear wheel speed sensors doing a brake job that included replacement of the backing plates and sensors. In the wiring diagram there were positive and a negative wires, could that be part of the problem?

bill in tomahawk

I believe I have finally gotten this sorted out. I took the van for about a 200 mile round trip to the high desert to go dirt bike riding today and the ESP lights remained off and everything worked well.

The smoking gun to my last problem was that the resistance on my wheel speed sensor went from 1.8Kohms to 0ohms whenever the connector was seated on the ESP module. There was, in fact, a short between the pins inside the connector - but only when the connector was seated. As I mentioned before, I brought this on myself when I disassembled the connector. I will repeat again - DON'T attempt to take this connector apart. In contrast, the ECU connector comes apart no problem, but not this one. The "fix" was to slide some harness tape (like electrical tape but without the adhesive) between the pins. As you can see in the attached pictures, these pins are similar to a molex connector in that there is a crimp to the conductor, to the insulation, and to the weatherproof seals. There is no insulation over the exposed crimp portion of the connector, so if you bend the pins trying to extract them they may short when you reinstall them.

Here are the lessons I learned that others may find helpful (although many are probably well known to regulars on this forum):
- If your ESP module goes bad, comes off the network, or you manage to somehow loose the signal from both rear wheel speed sensors, the transmission will not shift properly. It will stay in 1st gear until you repeatedly bang into the rev limiter at 4200 RPM, at which time you will finally get a shift into second. This is no way to drive long distances. This is because the only way the transmission module knows how fast the output shaft is spinning is from the rear wheel speed sensors. If you have at least one rear sensor working, and the ESP module can put data onto the CANbus, the transmission will work normally. If you have this affliction (no data from rear wheel speed sensors), you may also get very early and aggressive downshifting and the ABS pump may vibrate the brake pedal when you slow down below 5 MPH.
-This is probably a long shot, but consider that someone might have swapped the wiring between the left and right side wheel speed sensors when you are working through your troubleshooting. Mine were swapped and I probably would have sorted this out much faster if I had considered this a possibility. Before I figured this out, my testing made almost no sense.
- Never attempt to take the ESP (or other weatherproof connectors) apart unless you really know what you are doing.
-If all else fails and you are at your wits end, the definitive way to diagnose a speed sensor is to cut the wire (you have to do this to replace it anyway) and hook it to a scope and spin the wheel. The wheel does not need to spin very fast - by hand is plenty fast enough. For rear wheel sensors, you can put the axle on jack stands and cut both sides. Then you can put the car in drive and look at the signal on a scope, splice the wires back to the ESP module, switching left and right sides if necessary, to isolate the fault to the sensor or the wiring.
-For troubleshooting purposes, if you suspect a bad ESP module, you can plug your replacement module into the harness at the LF headlight without connecting any of the plumbing. It will communicate normally (but it wont be able to sense the brake pressure). This is a handy 1 minute test. Replacing the electronics can be done with slightly more effort, but without touching the hydraulics (pictures in next post).
-The wiring diagrams in the factory service manual at diysprinter may be incorrect for your vehicle. I cant find the wiring diagram right now to confirm, but my recollection is that it did not match the diagram in the Xentry. The Xentry absolutely did match my vehicle.

To summarize my problem, I think I had an intermittently functioning ESP module that would disappear from the CANbus and prevent the transmission from shifting out of 1st. Troubleshooting was complicated by that fact that during some previous "repair" the wires to the left and right side wheel speed sensors were swapped. I made things worse disassembling the ESP connector, which caused the pins to short inside the connector. With the connector "repaired," the rear wheel speed sensors now connected to their proper sides, and a junkyard ESP module my van is working for now.

The ESP connector appears to be attached to the main body harness and looks to be too difficult to replace. I will probably replace (solder on a new one) the ESP connector. The junkyard that I bought the ESP module did not have the connector. If anyone is parting our a T1N with ESP and wants to sell the ESP connector or harness, I'd like to buy it.

Photos below:

Some additional pictures:

99sport,
That was a great post. I have to admit that my understanding of the ABS/wheel speed sensor system is limited.
And I both had, and after reading your post, may still have a problem with my van.

Some History
This summer when traveling I would lose the cruise control and get the ARS light. Reading the codes indicated that wheel speeds were implausible. To further diagnose the problem I ended up doing a complete brake job including replacing the rear backing plates and both rear wheel sensors. Initially the new wheel speed sensors were both mis-adjusted and the vehicle went into limp and would not shift out of first gear. The sensors were readjusted,the codes went away and shifting returned to normal. Cruise control works.

But a slight problem remains, IF it is a problem. You described it above as a pulsing("...the ABS pump may vibrate the brake pedal."). Well, I have this symptom but no other problems. So to my question, "Could this be caused by the wheel speed sensors being reversed?"
That might have happened when the wires were cut.

If not what could cause it? It occurs when I brake to slow down in the last portion of the stop around 5 mph.
Honestly I didn't think thee system was that smart?

Any thoughts?

bill

billintomahawk said:

99sport,
That was a great post. I have to admit that my understanding of the ABS/wheel speed sensor system is limited.
And I both had, and after reading your post, may still have a problem with my van.

Some History
This summer when traveling I would lose the cruise control and get the ARS light. Reading the codes indicated that wheel speeds were implausible. To further diagnose the problem I ended up doing a complete brake job including replacing the rear backing plates and both rear wheel sensors. Initially the new wheel speed sensors were both mis-adjusted and the vehicle went into limp and would not shift out of first gear. The sensors were readjusted,the codes went away and shifting returned to normal. Cruise control works.

But a slight problem remains, IF it is a problem. You described it above as a pulsing("...the ABS pump may vibrate the brake pedal."). Well, I have this symptom but no other problems. So to my question, "Could this be caused by the wheel speed sensors being reversed?"
That might have happened when the wires were cut.

If not what could cause it? It occurs when I brake to slow down in the last portion of the stop around 5 mph.
Honestly I didn't think thee system was that smart?

Any thoughts?

bill

Click to expand...

Your symptoms are NOT caused by the polarity of the speed sensor wires being reversed. The speed sensor is a mini AC generator - it makes an Alternating Current sine wave with the frequency proportional to wheel speed. The current travels in both directions exactly the same amount of time. I know for a fact you can hook them up backwards and everything will work normally - I intentionally hooked mine up backwards.

The pair of wires going to the sensor has a black and a brown wire. My wiring was hacked up pretty badly by previous repairs (I even had a wire nut for one of the connections). On both the wires going to the ESP module and to the sensor, my black wire was about an inch shorter than the brown wire. Rather than cut an inch off of both of the harnesses and restrip everything and make my wires even shorter (they are already too short to reach the factory tie down locations), I simply connected the short black wire to the long brown wire - thus connecting the sensor "backwards." I soldered everything up and covered it in shrink sleeve as the service manual directs and everything works normally this way - the only downside is that it may be more confusing for whoever has to troubleshoot this later down the road. Since that will be me as long as this van is on the road, it should not be a problem (hoping I remember what I did if I ever need to work on this again).

Regarding your ABS pumping at low speeds, I don't have anything to offer at this point. My van no longer does it after the ESP fix, but I've only put 200 miles on it since it was fixed. I bought the van about 6 months ago with a host of problems, and the total distance I've driven with all of the dash lights OFF is probably less than one tank of fuel, so I am not an expert on how these vans are supposed to run.

One final thought, I had a check engine light for a bad MAF and, after verifying all the wiring was good from connector to connector, I found (based on a tip from Midwestdrifter - otherwise I probably never would have figured it out) that I had a socket inside the connector that was not making contact with the pin on the ECU. In other words, when I disconnected the connector to verify wiring, everything checked out, but the signal wasn't crossing that last connector. The ESP module connector has a completely different style of socket than the ECM (ESP sockets grip the pin on two sides, while the ECM socket is 4 sided), so hopefully it is less likely to make a bad connection. However, if you do find yourself troubleshooting wiring again, keep a bad pin to socket connection inside the connector as an option.

Bill: if the wheel sensor to tone ring clearance is a bit too wide the sensor signal will vanish at low speeds, which the module will interpret as a wheel lock and pump the brake, resulting in pedal vibration.
You can view the wheel speeds in ESP live data. Watch wheel rpm as you cruise at low speed. They should match (unless you’re turning, then the outside wheel should be faster) and both (all) should drop out at the same time. If one consistently drops out early, I would first try tapping the sensor in to reset the clearance, and if that fails check the tone wheel for flatness (remove the sensor and use a feeler to skim along the tone wheel as you spin the tire). High spots can be gently pushed down with a dowel.

Good luck,

-dave

Dave, I found that wheel speed data in my Autel MD 802 all systems and lost it, I searched in the scanner and could not find it again. Any clues as to where it hides?

And thanks 99sport, got it.

bill

Hi @Nautamaran. Thanks for your helpful post! I’m getting some intermittent “zero values” in some or all of my wheel speed sensors (per the ap200).

Nautamaran said:

and both (all) should drop out at the same time.

Click to expand...

May I ask for a clarification on what you mean by “drop out”? Do they “drop out” at a certain increased speed?