Misfire Vehicle Speed Sensor Disco 1

Chris-St Louis

Chris-St Louis

1
Oct 27, 2004
3,000
4
An intermittent VSS fault is identified by a freeze frame speed of above 110 mph (an input to GEMS caused by a noisy signal from the VSS), complaints of intermittent power loss, or engine stall.

NOTE: On TestBook disc DRG 0001 and DRG0002 the road speed displayed as "MPH" is actually a kilometers per hour value, NOT miles per hour. A TestBook reading of "177 MPH" is actually 177 kph. This reading, when converted to the desired mile per hour reading, is 110 mph.

One of the functions of the VSS signal to the GEMS unit is to provide information on vehicle speed. If the GEMS unit sees an excessively high speed (above 110 mph) it will initiate fuel cut off to the odd cylinders momentarily to reduce engine power. This feature is intended to prevent the driver from operating the vehicle at excessive road speeds.

Customer complaints of intermittent engine surging at highway speeds, inoperative or fluctuating speedometer, or a MIL illumination could be caused by an intermittently failing VSS.

If the MIL is illuminated with misfire codes P0300, P1316 and any combination of P0301, P0303, P0305 and P0307 stored or if the customer complaint is surging, hesitation, or loss of power at highway speeds, pay close attention to the freeze frame data, particularly engine rpm and road speed.

NOTE: As with all electrical diagnosis, the circuit between the sensor and the GEMS unit should be checked. The technician should be aware of the fact that the sensor test will not detect an intermittently failing sensor.

If the freeze frame data shows a road speed that does not conform to the engine speed (for example 110 mph at 2000 rpm or a road speed of 0 mph), an intermittent fault with the VSS could be the problem.

If inconsistencies between engine speed and vehicle speed are observed, replace the sensor. See attached DTCR samples
 
MUSKYMAN

MUSKYMAN

Well-known member
Apr 19, 2004
8,277
0
OverBarrington IL
OK?....just change the VSS and be done

gems has a 105mph limit on it so if all the sudden it gets a 110 signal from the VSS yes it cuts out the odd cylinders...most likely a bad VSS.

these things go bad all the time .

the last one I installed I sealed it on with ultra blue....its now been in there a real long time compared to the ones before it. I believe that contamination kills them. just wait and see...first real cold/frozen day there will be all kinds of VSS related posts. I believe thats because when they have been contaminated with water and it freezes they go bad.

...off my soap box :cool:
 
Chris-St Louis

Chris-St Louis

1
Oct 27, 2004
3,000
4
I just wanted to give some information so that people can confirm a failure. Not just guess because a Internet forum told them so.

Replacement on a hunch when there is a test proceedure avalible is hackery.
 
Mark

Mark

Member
Oct 14, 2004
15
0
Havelock NC
weldinghistory.org
I had my Actron 9145 readily available so when the engine started shuddering, I could attach the moniotr and check for the problem source.

Low and behold, I saw a disparity between the Spedometer and the Vehicle speed, generally around 8 MPH on the low side (sensor).

Just before the engine would shudder, the VSS signal became erratic, jumping up and down then shooting to 110+ MPH.

Confirmed...Repalcing Friday.

I was also getting the same MILS codes. Mine would occur if the weather was hot & humid. Otherwise I had no instances during the cooler winter months. Now that summer is here and nearly 6 weeks of Heat Indices in Eastern NC, the problem reared its ugly head ... again.
 
MUSKYMAN

MUSKYMAN

Well-known member
Apr 19, 2004
8,277
0
OverBarrington IL
well...i would check the exhaust joint in front of the muffler...when it leaks it can cook the wire harness and the VSS it self.

check it you might find the new source of failure

mm
 
Mark

Mark

Member
Oct 14, 2004
15
0
Havelock NC
weldinghistory.org
I thought of the that also - about excessive heat on the wire. The aluminzed shield is broken off just forward of the muffler, the rest is intact. After I replace the VSS, I am going to heat protect the pipe in that area to stave off future problems, I hope. Mine does not leak but I think the heat is sufficinet to cause the copper wires to heat up and reduce resistance making the engine think its travelling 110+ MPH.
 
jhmover

jhmover

Well-known member
Apr 23, 2004
5,571
3
California
I had the same problem. Replaced the VSS and problem gone. I'd go with Muskyman on the ultra blue, mine had 5 tons of oil on it. Mike at West Coast British said he removes them and squirts them with contact cleaner, puts them back and they work fine. Gives me the impession the oil causes most of the problems. I may pull mine, clean it and seal it as I'm convinced the oil getting into it is the problem usually, not that they don't eventually wear out as it's moving parts.

JH
 
P

parthog

Guest
Mine went bad, intermittant speedometer dropout and Cruise Control dropout. Intermittant. I replaced it with a new LR part, which lasted a week and quit entirely. Incidentally, the stealer tells me that they have to diagnose it as bad as a service appointment for me to get my $125 back, ... my DMM shows it as an constant open circuit.

Anyway, I cleaned and re-sealed the original one and it has been fine since (about 1,000miles).

The sensor ('99 D1, ~79,000miles) is a magnet spinning (4 revs per tire rev I believe) and there is apparently a reed-switch potted (sealed in RTV) in the end of it, if the reed switch goes bad there's no way to "clean it with contact cleaner" although cleaning the plug is possible. Mine was intermittant apparently because the cavity which contains the spinning magnet had popped open (sealed by urethene or silicone), possibly from moisture getting in and freezing, and the cavity was full of sand and dirt. Cleaning and re-sealing worked.

- Jeff Miller
 
ptschram

ptschram

Well-known member
Sep 27, 2004
21,955
49
In the shop doing the Lord's work one broken Rover
www.ptschram.com
parthog said:
The sensor ('99 D1, ~79,000miles) is a magnet spinning (4 revs per tire rev I believe) and there is apparently a reed-switch potted (sealed in RTV) in the end of it, if the reed switch goes bad there's no way to "clean it with contact cleaner" although cleaning the plug is possible. Mine was intermittant apparently because the cavity which contains the spinning magnet had popped open (sealed by urethene or silicone), possibly from moisture getting in and freezing, and the cavity was full of sand and dirt. Cleaning and re-sealing worked.

- Jeff Miller
Click to expand...

Jeff:
1: The VSS works on a Hall Effect sensor. ie-a spinning magnet induces a voltage in a sawtooth waveform. It is a non-contact sensor.

2: I have had more failures of brand new parts with this part than any other! I've had three of them fall apart during installation as the silicone isn't the most robust method of attachment. In spite of several years of searching, I've not been able to find a bolt-on substitute.

Someday, I'll build a VSS simulator for testing things like cruise control. Someday...

PT
 
E

Eah

Well-known member
Apr 20, 2004
119
0
Colorado
Vss

Does this apply only to D1's? I have the intermittent surging at highway speeds, but not speedo issues or SES light. I have a 00 D2.
 
Mark

Mark

Member
Oct 14, 2004
15
0
Havelock NC
weldinghistory.org
I had my VSS replaced today. The old one has the part number AMR 1253. The new number is YBE100540.

The mechanic said that when he unbolted the sensor, it fell apart.

I saved it for information purposes.


The rover ran smooooth...
 
E

Eah

Well-known member
Apr 20, 2004
119
0
Colorado
VSS Sensor

I hate to repost, but can someone tell me if there is a similar sensor in a 00 D2? I have the surging, but no SES light or a fluctuating speedo. Thanks
 
C Ross

C Ross

Well-known member
Aug 24, 2004
459
0
54
Oklahoma
MATT223081 said:
I need to replace my vss and i am on vacation, where is the part located and is this something i can do myself.
Click to expand...

Matt,

It's a very easy fix. Just don't overtighten the new part as it's somewhat delicate. Nothing like experience to learn that lesson. Good thing the dealer parts guy is a friend.

Ross
 
L

Len

Member
Jul 24, 2007
13
0
Williams Bay, WI USA
I'm having more or less the same problem as Eah with my 96 D1 in that when the VSS is plugged in it shutters and boggs down but no visible changed on the speedometer or tach. Rarely a check engine light but have experienced codes described by Chris above. I have already put a new VSS on and it still does the same thing. Also, there is no sign of damaged or melted wires by the plug.

The D1 also has the wheel speed sensors on each wheel. Are these directly or indirectly tied to the VSS on a D1?

If I unplug the VSS the truck runs better than ever but I obiviously don't have a speedometer or odometer.

Chris mentions checking the circuit....
"NOTE: As with all electrical diagnosis, the circuit between the sensor and the GEMS unit should be checked. The technician should be aware of the fact that the sensor test will not detect an intermittently failing sensor."

Where exactly would I look to test this? I've tried to trace the wires from the VSS forward but loose track when they get bundled up. I looked at pictures for the component locations and connection locations found in the Rave manual but still can't see where these two wires go or what they get attached to.
 
R

rovering

Member
Mar 3, 2010
13
0
Catacombs of the mind
Len said:
I'm having more or less the same problem as Eah with my 96 D1 in that when the VSS is plugged in it shutters and boggs down but no visible changed on the speedometer or tach. Rarely a check engine light but have experienced codes described by Chris above. I have already put a new VSS on and it still does the same thing. Also, there is no sign of damaged or melted wires by the plug.

The D1 also has the wheel speed sensors on each wheel. Are these directly or indirectly tied to the VSS on a D1?

If I unplug the VSS the truck runs better than ever but I obiviously don't have a speedometer or odometer.

Chris mentions checking the circuit....
"NOTE: As with all electrical diagnosis, the circuit between the sensor and the GEMS unit should be checked. The technician should be aware of the fact that the sensor test will not detect an intermittently failing sensor."

Where exactly would I look to test this? I've tried to trace the wires from the VSS forward but loose track when they get bundled up. I looked at pictures for the component locations and connection locations found in the Rave manual but still can't see where these two wires go or what they get attached to.
Click to expand...

So, I understand this is an old post, but did you ever trackdown this problem? I'm having similar issues and would like to know. :banghead:
 
ptschram

ptschram

Well-known member
Sep 27, 2004
21,955
49
In the shop doing the Lord's work one broken Rover
www.ptschram.com
LOL, Monday, morning, I took my son to the train station and on the wayhome, my '88RRC quit! Knowing I've got a wonky fuel gauge, I dumped the five gallons I carry into the tank and drove on.

It happened again! And seemed to be worse when I hit the rumble strips on the edge of the road.

I got it home and thought I'd found the problem as the coil wire was rubbing on the alternator pulley/fan.

Ran to NAPA and clearly, that wasn't the problem. Before leaving NAPA, I crawled benath the truck and disconnected the speed transducer (VSS on early trucks). Voila! No misfires!

I was pretty surprised as this was the first time I'd seen one that was wonky at pretty much all speeds. I was preparing to look at vacuum advance, plugs, wires, ignition amp, etc and merely unplugging the transducer seemed to have resolved the issue.

The first stop sign I came to the engine died as it wasn't sure what to do wit the IAC, I'm sure, but once it figured that out, it hasn't been an issue, but I do plan to replace the trasnducer this afternoon.

FWIW-I have a brandy new VSS for a DI, genuine Land Rover in the box.
 
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