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Old 11-10-2015, 05:01 PM
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Post Speedometer Error - Fuel Shut Off - Lurging

FYI: My speedometer registered about 3 times the actual speed, e.g. driving 35 mph actually indicated about 105 mph. When my 2003 Wrangler Rubicon TJ reached a certain speed threshold, the fuel would be cut off, which resulted in a 'lurching' of the Jeep. The Jeep would slow down, and then fuel was restored.

The problem began after the battery died. I tried to clutch start the engine on a flat parking lot but could not get up enough speed. I received a jump, and initially there were some sparks on the other vehicle. We rechecked the connections, and they were correct. The next attempt resulted in a successful start.

The solution was to, at least, replace the alternator. My best guess is that the alternator has an internal diode bridge rectifier and a capacitor or capacitor bank to output a DC voltage. When jumping the Jeep, the negative cable on the other vehicle (Toyota Land Rover) sparked, which meant that there was a high current discharge due to unequal ground voltages on the two vehicles. The high current probably damaged one or more of the diodes and/or one or more capacitors in my alternator. The result may have been that the alternator was putting noise on the ground plane that was affecting the PCM and/or the speed sensor signal. The mechanic diagnosed the problem by taking the alternator out of the circuit and either checking the ground voltage or driving the vehicle. Regardless, the problem went away when the alternator was disconnected. Before replacing the alternator, the speed signal sensor, the clutch position sensor, and the PCM were all replaced. So, I'm not certain whether any of the replaced devices in addition to the alternator were also contributing to the solution.

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Old 12-26-2015, 09:39 AM   #2
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Question Same speedometer problem 03 Rubicon

I wish someone had replied to your inquiry because I just had the exact same problem with my 03 Rubicon. I took the battery out so that I could put a new one in. It was out 2-3 hours while I went to the store to pick up the new battery. Put the new battery in and went for a drive and was already doing 75 miles per hour in my driveway. Seems to be registering 3-4 times actual speed. I'm afraid to drive it normally until I get in fixed because I don't want to damage the speedometer. Thought maybe I should just put a new speed sensor in but decided to check the forum first. Seems to be little out there on this particular problem but I'll keep looking and hope someone responds.

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Old 12-26-2015, 10:01 AM   #3
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He did not ask a question he shared a problem and how he solved it so why would someone respond

Yes the Rubi has a speed sensitive cutoff

No high readings will not hurt speedo

it is a problem with tone ring or speed sensor or noise in the circuit

Yes somewhere in the range of 90 to100mph Rubi speed limiter kicks in

If a manual could just uplug speed sensor and try driving like that but if a damn slouch box will be drivability issues

Could noise from bad alternator be a cause his experience suggests it can but speed sensor gets three wires
Sensor ground from PCM
5 volts from PCM to poser sensor
Sensor signal wire to PCM

So guys added boxes to recalibrate sensor signal for gears and tires and some of those boxes have caused intermittent high speedo readings

If you have one find it by following harness from speed sensor at back of transfer case output
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Old 12-27-2015, 10:19 PM   #4
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Same speedometer problem 03 Rubicon

Thanks Digger84 for the info. As this is my first post I guess I assumed on the first post someone would have responded. Sorry my mistake. I checked to see if there is any calibration box and I don't see any. Sensor is hardwired with about a 12 in pigtail that goes to the plug mounted on top of the trans case. That plug is wired directly into the vehicle wiring harness. Could that calibration box be mounted somewhere else? The Jeep has 33's on it and the speedometer was reading within one mph according to my GPS. Only have driven this Jeep a few time since I bought it a few weeks ago. There were no speedometer problems until I removed and replaced the battery. I'm going to clean all of the grounds and the plug on the speed sensor. Hope it's something that simple but it rarely is.Will check and post response tomorrow.
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Old 12-28-2015, 12:14 PM   #5
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Well it's definitely not the grounds. Never is simple so I went ahead and did the speedometer cluster self check and everything is normal. Thanks Digger84 for that video. Never knew you could do that. Next I checked voltage at the speed sensor. There is 5 volts on both pos and PCM side and a good ground with ignition in run position but not started. Is that correct? Does that lead you to suspect a bad sensor? I have read that the Rubicon's have to have the speed calibrated in the PCM. Is it possible the PCM lost the calibration since the battery was disconnected for a few hours? I have looked at several auto parts stores and none of them show the type of speed sensor like the one on my Rubicon even Rock Auto. Mine is a hard wired sensor with a 12" pigtail that goes up to the vehicle wiring harness. All the ones I've seen are molded plastic and the wiring harness plugs into them. Even the sensor part is different. Not sure if this is an aftermarket or just Rubicon specific. Any help there is appreciated also.
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Old 12-28-2015, 12:35 PM   #6
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The Rubicon's speed sensor is different since there's no speedometer gear in a Rubicon transfer case, it uses a heavy three-node steel tone wheel mounted on the output shaft to generate the pulses in the sensor. The sensor is probably a Hall Effect which means it's just a coil inside its enclosure so if there's 5v on one side, you'd see 5v on the other side too... neither side gets grounded on a Hall Effect sensor.
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Old 12-28-2015, 01:12 PM   #7
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The sensor has three wires plus 5 ground and signal as when you add a speedohealer, like I did you T into plus and ground and run the signal thru the box

By T-ing into plus 5 and ground you get power for the speedo healer box
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Old 12-28-2015, 01:53 PM   #8
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OK thanks. So it's not a programming issue? I did a google search and found the correct sensor for anyone interested that may read this. The Chrysler # is 5033202AB, Airtex Wells SU3344 or 5S4942, Standard Motor Products SC332. Any recommendations on a speedohealer box or where to get them?
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Old 12-29-2015, 10:44 PM   #9
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Question

After reading several more hours of threads and googling this problem I tried the PCM reset with no luck. I've removed and cleaned the sensor and plug, cleaned all of the grounds and checked the voltage at the plug on the transfer case. I hate throwing money at I problem I can't first diagnose. I'm starting to think more on the lines of the initial thread that possibly the alternator may be creating the "noise". When the battery went dead I used my 200 amp jump starter to start the Jeep. Maybe a diode fried causing the problem. I'll check charging voltage tomorrow. Is there any way to take the alternator out of service to see if that is causing the problem?
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Old 12-30-2015, 07:20 AM   #10
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Yes but be very careful

If you have a good fully charged battery and disconnect wiring at alternator and insure wires adequately taped off to prevent grounding

Then with no AC or heater fan, no radio, and no lights could easily do a test drive on battery power

However if you attempt to reconnect alternator wiring while engine is running you can create a very brief voltage spoke that could permanently damage the PCM

Did the mishap with jumping or charging happen just before the erratic speedo readings started

If so perhaps they are at least related
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Old 12-30-2015, 10:26 AM   #11
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That third wire is called sensor return and besides the speed sensor it is spliced to oxygen sensors, clock spring, throttle position sensor, batter temp sensor, intake temp sensor and others

To quote the FSM (TJ 1998 FSM page 14-34)
Sensor Return - PCM Input
Sensor Return provides a low noise ground reference for all engine control system sensors

Similar but different is
Signal ground which provides a low noise ground to the data link connector
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Old 12-30-2015, 01:09 PM   #12
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Yes, the speedometer error occurred right after jumping. I only moved it a few feet so I could get my truck out so I didn't notice the speedometer error. I then removed the battery and took it with me to the store. As soon as I put the battery in and drove it I noticed the speedometer was way off.
I did disconnect the alternator this morning but there was no change. Speedometer still reading 3 times actual speed. I'm still not understanding why both the pos wire and PCM wire would both be reading 5 volts with the sensor unplugged. Is this from other sensors? How does the PCM differentiate the signal from the speed sensor and all the other sensors? Is it through the ground - wire? Sorry for asking so many questions but my last Jeep was a YJ and much less complicated in many respects. Thanks!
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Old 12-30-2015, 06:01 PM   #13
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Three wires to sensor

plus five constant supplied by PCM to several sensors

Ground that is a sensor common ground connected to PCM

A signal wire for just the speed sensor
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Old 12-30-2015, 06:29 PM   #14
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Old 12-30-2015, 06:37 PM   #15
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Read next to last post in TJ General thread
Jumping speedometer driving me nuts

The sensor ground shared by oxygen sensors was grounding to metal where insulation was scraped off

The sensor ground needs to be an isolated feed from the PCM
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Old 12-30-2015, 08:53 PM   #16
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I will check these tomorrow as well as the ABS sensor wiring. I've also read where dealers had success with the PCM reset but had to do it several times before the speedometer started working properly. Will try that as well but the sensor wiring seems to make a lot of sense. Thanks!
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Old 01-01-2016, 11:08 AM   #17
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Question

Well I checked all of the sensor wiring under the vehicle, ABS and 02, and didn't find any grounded but did find a few severely pinched on the ABS mount on the transfer case skid plate. Wouldn't a grounded sensor throw a code? I ordered a new speed sensor from Rockauto.com. That's the easiest and least expensive way to try to fix problem. It does have 180K miles on it. It'll take a few days before it gets here and I get it installed. Nobody seems to show the right part for a 2003 Rubicon. Even Rockauto is wrong for 2003 and 2004. You have to go to a 2005 to get the correct speed sensor and then you have to be careful because they show both types. Several are for the NP231 transfer case and the last two or three are for the NV241. If that doesn't work then the only alternative at this point is the speedohealer unless someone has any other ideas. I'd rather fix the problem then mask it. I've read on other threads that if the tone ring is removed and not installed properly in the slot for the output shaft pin, then errors may occur. I don't know what kind of work previous owners performed so I don't know if this is a possibility. Here is an interesting link on the Hall Effect Sensors and how they work. https://en.wikipedia.org/wiki/Hall_effect_sensor Thanks Jerry Bransford for that information. It looks like there are three common speed boxes. Yellow Box V5, Dakota Digital SGI-5E and Speedohealer V4. Anybody have any recommendations to either buy or stay away from? Hypertech also make a speedometer calibrator for reflashing the computer. Anybody ever try this? All help and comments are greatly appreciated. Thanks and Happy New Year!
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Old 01-02-2016, 07:30 AM   #18
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You do know all the TJ use an electronic speed sensor but all but RUBI and aftermarket super short SYE use a gear before the sensor

Which is why just wire splices is all you need when using a tone ring speedo sensor on an TJ that had the gear driven setup like my 98 sport with a super short SYE

I still think it is much more likely noise in the wiring and of so neither a new sensor or a speedo healer will fix it

You could try a test run with sensor unplugged and see if speedo stays at zero

Course if you have auto/slush box it may mess with the shift points
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Old 01-02-2016, 09:32 AM   #19
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That's a good idea! It's a manual trani so I'll unplug it and see if I'm getting any speedo movement. It'll be a few days before sensor is here anyway. We had about a foot of snow over the last 2 days and I hate to get it all slopped up if I have to work on it. Maybe I'll just do it on the lift. I should see something as soon as the wheels start to spin.
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Old 01-02-2016, 09:52 AM   #20
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Well you should see nothing but if it is wiring it would still intermittently jump as often as before
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Old 01-02-2016, 01:16 PM   #21
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There's nothing intermittent about it. The speedometer increases smoothly as if driving a Ferrari. Only problem is you're doing 30 when the speedo reads 90. Tach is normal so only speedo is affected. 1st gear about 30, 2nd gear about 60 and so on. Just reading 3 times normal which is why I initially thought is was a programming issue. I'll try running unplugged later. Just got the driveway snowblowed.
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Old 01-02-2016, 01:30 PM   #22
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Well if a constant error like always 3 times normal value a speedo healer would solve that
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Old 01-02-2016, 02:35 PM   #23
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Well no luck unplugging the speedometer. Reads 0 at all times. I don't know if that proves there is no noise or short in the sensors. Guess I'll just wait until the new sensor gets here and take it from there.
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Old 01-07-2016, 04:15 PM   #24
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Well I put the new sensor in today and no change. Now I'm pretty convinced that it's a programming issue. Question is do I let the dealer reflash the computer or just put the speedohealer in and hope that fixes it. Not sure what a dealer would charge to reflash the computer but I'll give them a call tomorrow and find out. I talked to the guy I bought it from to get a little more background on the Jeep. It was built and sold in Canada and brought to the US a few years ago. Pretty common in this area where Canada is only a few miles away. A new speedometer was installed for MPH instead of Kilometers. The computer was probably reflashed for this change. When the battery was removed or when I reset the PCM it went back to the PCM's original configuration which was kilometers. This is only a theory at this point but seems to make sense.
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Old 01-07-2016, 06:44 PM   #25
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I don't think there is any PCM adjustment programming for speedo

For non Rubi they just change speedo gear size no programming

For Rubi they were all 4.11 and all had same size tires from factory so no change in PCM program was needed as a matter of fact they all read fast and odometer was over reading miles some speculate because was setup for 33 inch tires planned for Rubi but pulled late in process

Still think noise in system or something like a loose tone ring but for just ratio programming a speedo healer is the ticket as easy to install and highly adjustable

I run one on my 98 sport that has a super short SYE so just a tone ring and easy to adjust when I swap from my 31 snow tires to 33 summer tires

But you can always see how much the stealership wants to attempt to correct

Never have taken my vehicles to a stealership for repair guess I am
Just too cheep
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Old 01-20-2016, 08:47 AM   #26
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Well winter has hit with a vengeance lately and I don't drive my Jeep on the roads once they start dumping salt on them so it may be a while before I wrap this up. For the cost of the dealer flashing the computer I can buy a speedohealer. I found them on e-bay but they currently don't have one listed for a TJ, at least not the plugnplay unit. They seem to go quick so must be a common issue. Once I get it installed I won't be able to fine tune it until the roads clear up a bit. Should need to be about -65% to start. I can tell on the lift if it's going to work.
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Old 01-31-2016, 02:09 PM   #27
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Smile Finally Fixed!

As I suspected from the beginning, the problem was the PCM calibration for kilometers. Being a Canadian Jeep, the PCM was calibrated in kilometers. When the battery was removed and/or the PCM reset was done, the PCM reverted back to its original calibration in kilometers. I did install a SpeedoHealer but only had to turn on the Km/MPH conversion to have the speedometer read correctly. It was more expensive than having the PCM reflashed but this will prevent this from happening again and also gives the flexibility to change tire sizes and adjust speedometer for them. I bought the plugnplay kit (e-bay) and opted to run the wire through one of the rear seat drain plugs and mount the box inside next to the driver seat to make changes a breeze and keep the electronics out of the muck. Hope this helps someone down the road. Lesson learned? Keep a 12 volt supply on the vehicle if battery is removed for any period of time! Thanks everyone for your help and input!
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Old 01-31-2016, 04:25 PM   #28
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Glad fixed but doubt the km story for 2 reasons

kM clusters are different part number with different display

Cannot see hitting Rubi speed limiter at that speed in kilometers/hr Way too slow an actual speed to be cutting off engine

Maybe some hybrid confusion kanook vs federal but at least it is working

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