Does any one have detailed info about how the RWAL system works? Diagrams and logic charts? By this I mean what are the voltages supposed to be on each connector pin and what sort of signal is expected. Then what combination of conditions on these connectors causes the computer to decide to turn on the ABS warning light? If I knew the details of how the electronic logical and electrical system worked I might be able do devise a fix for my false warning light condition. I've cleaned every connection and tried every fix anyone on these forums has come up with and I still get the warning light. I'm suspecting that I am getting a transit voltage spike to cause a false alarm.
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RWAL sytems?
- Thread starter Joe G.
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If the ABS lite comes on there should be a code stored in the module. Codes can be check on the 95 RWAL system by grounding the diagnostic connector under the dash near the steering column area, it will be a small black plastic connector that can hold two terminals but there is only one in it, it will have nothing plugged into it. There is another identical connector with two terminals in it under the dash also, so find the correct one with only one. With the key on, momemtarily ground the single terminal and the ABS lite should begin flashing, count the long flash and the number of short flashes, the long-short sequence will continuously repeat. Repost with the code and I will reply. In order to get the lite to quit flashing you'll need to unplug the module, it is located in the dash low and in the center. Remove the knee bolster from under the steering column and look to the right for a black plastic module with a single 14 wire connector and unplug it for a few seconds, this will reset the module.
Sorry this is long but I'll try help figure out what's going on,
HTH
Wayne
Sorry this is long but I'll try help figure out what's going on,
HTH
Wayne
Wayne,
I've done all that. What I'm trying to find out is how the thing works as far as expected signals and voltages are concerned so I can figure out how to prevent the bogus warning light and codes. The error is caused by something interfering with the RWAL logic. When the bogus error condition is detected the RWAL system sets an error code, shuts down RWAL, and turns on the warning light. Finding out what the bogus error code is does not help in correcting the problem.
I've done all that. What I'm trying to find out is how the thing works as far as expected signals and voltages are concerned so I can figure out how to prevent the bogus warning light and codes. The error is caused by something interfering with the RWAL logic. When the bogus error condition is detected the RWAL system sets an error code, shuts down RWAL, and turns on the warning light. Finding out what the bogus error code is does not help in correcting the problem.
Wayne,
Something is basically wrong with the system. A lot of people have this same problem. I suspect that it is too sensitive to inputs on the various connections. So it gets what appears to be a bad condition and sets an error code that is not correct. What I am trying to find out is what sort of signal(s) or voltage(s) cause it to detect an error. If I can get that kind of information then maybe I can figure out what to do to mask it from conditions that are wrongly detected as an error. If for example it is expecting 8 volts on a connection and is getting a transit voltage spike of 12 I can build filter to remove the spikes and still correctly detect the error.
Something is basically wrong with the system. A lot of people have this same problem. I suspect that it is too sensitive to inputs on the various connections. So it gets what appears to be a bad condition and sets an error code that is not correct. What I am trying to find out is what sort of signal(s) or voltage(s) cause it to detect an error. If I can get that kind of information then maybe I can figure out what to do to mask it from conditions that are wrongly detected as an error. If for example it is expecting 8 volts on a connection and is getting a transit voltage spike of 12 I can build filter to remove the spikes and still correctly detect the error.
Joe,
If you could let me know what code is being set in error it will help me understand what area we are looking at. There are thirteen fault codes dealing with various aspects of the system. There is no point getting into how the controller runs diagnostics on the isolation or dump solenoids if they aren't involved in you specific condition.
I am willing to try help but can't be much good if I don't know what's going on.
Wayne
If you could let me know what code is being set in error it will help me understand what area we are looking at. There are thirteen fault codes dealing with various aspects of the system. There is no point getting into how the controller runs diagnostics on the isolation or dump solenoids if they aren't involved in you specific condition.
I am willing to try help but can't be much good if I don't know what's going on.
Wayne
Wayne,
I have a service manual with all 15 fault codes (1 & 12 are not used leaving 13). I've checked the possible causes of a fault as much as possible. The most often fault (but not the only one) is 10, "Sensor wiring/resistance (usually low reading)". I have replaced the wiring from the sensor with a twisted pair as was suggested by someone some months ago. I have cleaned every connector involved with the sensor. It's RWAL not the full ABS so the sensor involved is the one in the rear differential housing. I've replaced that sensor. I have also cleaned the connector on the unit attached to the master cylinder several times. In short, I've taken the diagnostic and corrective steps I can take without knowing the details as I mentioned above. since this problem is pretty wide spread and attempts to get it fixed at Dodge dealers have not worked there is something basically wrong with the system. At the minimum I hope to be able to rig a push button so I can reset it when the warning light comes on. I hope to understand what is causing the incorrect error detection in the first place. I don't want to throw parts at it in the hope it goes away.
I have a service manual with all 15 fault codes (1 & 12 are not used leaving 13). I've checked the possible causes of a fault as much as possible. The most often fault (but not the only one) is 10, "Sensor wiring/resistance (usually low reading)". I have replaced the wiring from the sensor with a twisted pair as was suggested by someone some months ago. I have cleaned every connector involved with the sensor. It's RWAL not the full ABS so the sensor involved is the one in the rear differential housing. I've replaced that sensor. I have also cleaned the connector on the unit attached to the master cylinder several times. In short, I've taken the diagnostic and corrective steps I can take without knowing the details as I mentioned above. since this problem is pretty wide spread and attempts to get it fixed at Dodge dealers have not worked there is something basically wrong with the system. At the minimum I hope to be able to rig a push button so I can reset it when the warning light comes on. I hope to understand what is causing the incorrect error detection in the first place. I don't want to throw parts at it in the hope it goes away.
It is entirely possible that you are having a different problem than others are having when their ABS light comes on. If you are all getting the same code then maybe you do have the same cause. But if the codes are different then it is much more likely that you have different problems. The first thing to do when the ABS light comes on is to check to see if there is a code. If there is not then you have much more of a problem. The code almost always tells you what circuit to be concerned with. For example, You did quite a bit of work to the Speed sensor circuit. If the code was for that circuit there are still several things that can cause that code that are still not checked. One thing I would do is check the output voltage coming out of the sensor. This voltage needs to be of the proper consistency and voltage level. The best way is to look at it with a oscilloscope,. That sensor produces a A/C sine wave. The sine wave needs to be consistant from wave to wave and be of sufficient amplitude for the computer to decifer it. Each wave is caused as a tooth on the ring in the differential passes the sensor.
That is just one possibility on one circuit. All I am saying is that you need to narrow it down first then analyze it. And on the other hand , it's none of my business, just trying to help
That is just one possibility on one circuit. All I am saying is that you need to narrow it down first then analyze it. And on the other hand , it's none of my business, just trying to help
Thanks for your help, but the purpose of this post is to see if anyone has the technical information that I want. It is NOT to get help or suggestions about how to diagnos the RWAL. Nor do I want a discussion of trouble shooting the thing. I am trying to get some technical information here. I want to know the details about how it works and what the signals and voltages are as I asked in the first post in this thread.
Things I *do* know about the CAB from having put a scope on it:
- Pins 1 and 8 are from the rear wheel sensor; one is connected to ground and the other is ocnnected to the sensing circuit. Since the rear sensor is not read as a differential signal, twisted pair cable is not needed. This signal varies from about 300mV at near stop to about 2V at 35 MPH and above. Lower than about 300mV, the CAB shouldn't 'see' the signal.
- Pin 12 is the VSS signal going to the PCM; it is a 0-5VDC square wave, open collector (the PCM must supply 'high' voltage to the CAB.
Things I've gleaned from the SM:
- Pins 3 and 10 are the CCD data bus/network.
- Pins 4, 7 and 14 are, essentially, battery voltage.
- Pins 6 and 13 are ground.
- Pin 2 is connected through the 4x4 switch to ground.
- Pin 9 is connected through the stop lamp switch to ground
- Pin 11 is connected through the brake pressure switch to ground.
- Pin 5 appears to be unused.
If you've verified that the rear speed sensor is putting out adequate voltage, the only other thing I can think to check is the CCD bus wiring. If the PCM cannot communicate with the CAB, I think it turns on the ABS light by sending a message to the dash cluster via the CCD bus. (Of course, now that I read through the SM, I can't see where either the CAB or the PCM controls the ABS lamp!)
What else was there? ... Oh, yeah. On my '98, if CAB pin 12 is not connected to the PCM, the ABS light comes on. I don't have an earlier SM, so I have no idea what pin 12 does on *your* CAB.
Of course, this is from my '98 12V SM, so things are a *little* different. E. g. , your older truck will have the VSS coming directly from the trans instead of out the CAB's pin 12. You might not have the 'digital' instrument cluster.
About all I can tell you!
Good luck!
Fest3er
Thanks for that Neal,
I would like you to decode your abbreviations so I know for sure what you are referring to. My '95 may not have the same boxes. It's kind of electronic illiterate. What kind of signal do you see on pins 1 and 8 when the rear wheels are turning vs stopped? Is the square wave on pin 12 a timing wave or does it vary with speed? Any amplitude change with any of these because of speed?
I have the service manual so I know what connects to what. I just don't know what is going on or supposed to be going on with the various circuits. I know that if I disconnect something the ABS squawks about it. This problem occurs on RWAL only systems as well as the all wheel ABS so it must be something in RWAL. I suppose I could rent a scope and take a bunch of tests and try to reverse engineer the logic but I don't want to try that. Do you know of any description of the logic involved in the boxes that causes an ABS fault to be dropped?
Thanks again.
I would like you to decode your abbreviations so I know for sure what you are referring to. My '95 may not have the same boxes. It's kind of electronic illiterate. What kind of signal do you see on pins 1 and 8 when the rear wheels are turning vs stopped? Is the square wave on pin 12 a timing wave or does it vary with speed? Any amplitude change with any of these because of speed?
I have the service manual so I know what connects to what. I just don't know what is going on or supposed to be going on with the various circuits. I know that if I disconnect something the ABS squawks about it. This problem occurs on RWAL only systems as well as the all wheel ABS so it must be something in RWAL. I suppose I could rent a scope and take a bunch of tests and try to reverse engineer the logic but I don't want to try that. Do you know of any description of the logic involved in the boxes that causes an ABS fault to be dropped?
Thanks again.
Joe,
The info posted by fest3er does not apply to your truck at all, the system layout, wiring and pin locations completely changed around 97 or 98 and newer.
Dodge printed no new info after the 89 RWAL diagnostic manual. So nothing new came out from 90 thru 96. Even though there was some minor changes.
What other codes have come up and how often?
How often does code 10 set?
What I can come up with for Code 10 (Sensor/wiring resistance unusually low) is pretty poor. Dodge figured us techs didn't need to know any more then they wanted us to, if it wasn't in the diagnostic manual you didn't need to know it- WRONG, we had to play with working vehicles to see what was normal.
I believe the module should be sending out a small diagnostic voltage to test the harness and sensor and monitoring what comes back. The sensor itself does produce an AC sine wave for monitoring rear wheel speed(which requires a twisted pair of wires to keep the signal clean), that signal can be checked with a lab scope, Code 6 would set if the reading was present but erratic. The low resistance code should mean that the diagostic voltage is not dropping (lowering) going back to the controller, essentailly an short circuit. The sensor should act as a load and drop some of the voltage before returning, the sensor resistance should be 1000 - 2500 ohms. I'm not sure if this is only done during Self Check with initial Key On or if continuosly while driving. You'd think only on Self Check, but again I'm not sure. I may be all wrong. Most of this isn't from a manual, it's based off of how typical circuits work.
I will drive my 94 gasser to work (Friday?) and test what's going on with pins 13 & 14, as my system works correctly and repost with that data.
More later,
Wayne
The info posted by fest3er does not apply to your truck at all, the system layout, wiring and pin locations completely changed around 97 or 98 and newer.
Dodge printed no new info after the 89 RWAL diagnostic manual. So nothing new came out from 90 thru 96. Even though there was some minor changes.
What other codes have come up and how often?
How often does code 10 set?
What I can come up with for Code 10 (Sensor/wiring resistance unusually low) is pretty poor. Dodge figured us techs didn't need to know any more then they wanted us to, if it wasn't in the diagnostic manual you didn't need to know it- WRONG, we had to play with working vehicles to see what was normal.
I believe the module should be sending out a small diagnostic voltage to test the harness and sensor and monitoring what comes back. The sensor itself does produce an AC sine wave for monitoring rear wheel speed(which requires a twisted pair of wires to keep the signal clean), that signal can be checked with a lab scope, Code 6 would set if the reading was present but erratic. The low resistance code should mean that the diagostic voltage is not dropping (lowering) going back to the controller, essentailly an short circuit. The sensor should act as a load and drop some of the voltage before returning, the sensor resistance should be 1000 - 2500 ohms. I'm not sure if this is only done during Self Check with initial Key On or if continuosly while driving. You'd think only on Self Check, but again I'm not sure. I may be all wrong. Most of this isn't from a manual, it's based off of how typical circuits work.
I will drive my 94 gasser to work (Friday?) and test what's going on with pins 13 & 14, as my system works correctly and repost with that data.
More later,
Wayne
Wayne,
The biggest reason I'm trying to get information (theory of operation description kind of thing) is that I'm tired of try this, try that and hope it's fixed kind of thing. So if I understand what the signals and voltages are supposed to be on the various connectors and what decisions the logic makes in response to these signals I may be able to bread board up something to control it.
I know how to prevent it from happening most of the time on my truck. This does not work all the time. When I start it up in my garage and let it idle for a bit while the torque convertor fills up it will usually light up the ABS warning light. After I back out of the garage I can shut it down while I close the garage door and put the cell phone whip back on top of the cab. If I do that and start to move as soon as I start it back up the light stays off. I usually drive the first two miles from in front of my garage without once touching the brakes. If I do (there is a yield sign) it makes no difference. Once in a while if I have to wait for a traffic light very long the ABS light will come on. Most of the time it won't. Very seldom it will light up while I'm just driving along. It used to do that quite a bit. I haven't looked at what codes it's making in quite a while because I'm trying to get information on how it works before messing with it any more. It was almost always 10 before but once in a while it was something else but I don't remember. I've never had the light come on as a result of brakeing hard or normal use of the brakes. Either sitting at idle with or without (trans in park) my foot on the brake or just driving along. Speeding up the engine has no affect, but if I can creep a little once in a while if I'm stopped at a light it will not light up. No more try this and try that. I'll just ignore it rather than do that anymore.
The biggest reason I'm trying to get information (theory of operation description kind of thing) is that I'm tired of try this, try that and hope it's fixed kind of thing. So if I understand what the signals and voltages are supposed to be on the various connectors and what decisions the logic makes in response to these signals I may be able to bread board up something to control it.
I know how to prevent it from happening most of the time on my truck. This does not work all the time. When I start it up in my garage and let it idle for a bit while the torque convertor fills up it will usually light up the ABS warning light. After I back out of the garage I can shut it down while I close the garage door and put the cell phone whip back on top of the cab. If I do that and start to move as soon as I start it back up the light stays off. I usually drive the first two miles from in front of my garage without once touching the brakes. If I do (there is a yield sign) it makes no difference. Once in a while if I have to wait for a traffic light very long the ABS light will come on. Most of the time it won't. Very seldom it will light up while I'm just driving along. It used to do that quite a bit. I haven't looked at what codes it's making in quite a while because I'm trying to get information on how it works before messing with it any more. It was almost always 10 before but once in a while it was something else but I don't remember. I've never had the light come on as a result of brakeing hard or normal use of the brakes. Either sitting at idle with or without (trans in park) my foot on the brake or just driving along. Speeding up the engine has no affect, but if I can creep a little once in a while if I'm stopped at a light it will not light up. No more try this and try that. I'll just ignore it rather than do that anymore.
This may not be relevant to your problem, but I'll add this anyway.
I have a 92 Dakota that had set the AWB light randomly for years. It had been to the dealer many times with no fix. 8-10 months ago I carefully bled the master cylinder and got a little air. It has not turned the light on since. It use to be eratic and anoying.
fox
I have a 92 Dakota that had set the AWB light randomly for years. It had been to the dealer many times with no fix. 8-10 months ago I carefully bled the master cylinder and got a little air. It has not turned the light on since. It use to be eratic and anoying.
fox
Joe,
Thanks for the info on when the code sets. I basically understand what info your asking for but I have no idea where to find it, short of getting a hold of someone in DC or Kelsey Hayes engineering. I have been a Chrysler tech for 8 years and have been teaching at a vocational college for the last 6, and I teach ABS. So I do have some knowledge base of ABS.
It appears that the light comes on when sitting still. To me, that makes sense on how I expect the circuit to work. When the vehicle moves the controller is looking at the AC signal generated by the speed sensor. Appearantely when there is no AC signal (not moving) the controller is testing the integrity of the harness and sensor circuit.
As I mentioned last time I will check my other truck to see what the diagnostic voltage is leaving and returning to the controller and post what I find (should be on Friday).
If you don't want this info let me know.
Wayne
Thanks for the info on when the code sets. I basically understand what info your asking for but I have no idea where to find it, short of getting a hold of someone in DC or Kelsey Hayes engineering. I have been a Chrysler tech for 8 years and have been teaching at a vocational college for the last 6, and I teach ABS. So I do have some knowledge base of ABS.
It appears that the light comes on when sitting still. To me, that makes sense on how I expect the circuit to work. When the vehicle moves the controller is looking at the AC signal generated by the speed sensor. Appearantely when there is no AC signal (not moving) the controller is testing the integrity of the harness and sensor circuit.
As I mentioned last time I will check my other truck to see what the diagnostic voltage is leaving and returning to the controller and post what I find (should be on Friday).
If you don't want this info let me know.
Wayne
Wayne,
Any info on how it works is appreciated. If it is something I can test with a meter so I can tell if the condition is within specs or not is part of what I'm looking for. I'm just tired of throwing fix attempts at the problem with no knowledge to back up the effort. I know enuff about electronics that if I can get the information I'm looking for I can figure the whole mess out. I don't have a scope right now, but I can get one if I need it.
Fox,
Thanks for that. This problem has been there for some time. I have flushed the brake system a few times as part of normal maintenance. No affect on this problem.
Any info on how it works is appreciated. If it is something I can test with a meter so I can tell if the condition is within specs or not is part of what I'm looking for. I'm just tired of throwing fix attempts at the problem with no knowledge to back up the effort. I know enuff about electronics that if I can get the information I'm looking for I can figure the whole mess out. I don't have a scope right now, but I can get one if I need it.
Fox,
Thanks for that. This problem has been there for some time. I have flushed the brake system a few times as part of normal maintenance. No affect on this problem.
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Subscribe
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