 | Home > Td5 > TD5 throttle position sensor |
 
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| diesel_jim Member Since: 13 Oct 2008 Location: hiding Posts: 6074   
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It's not the hi-low range switch stuck is it? try unplugging it from the top of the transfer box and see if that's any better.
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17th Apr 2013 3:33pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17218 
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The syptoms you describe really don't sound at all like the TPS failing.
I had the TPS malfunction on my TD5 Disco (as far as I know it's the same set-up as a Defender) and the symptoms were more like a classic misfire or flat spot. There are either two or three separate resistive tracks inside the TPS, and as the throttle is depressed one channel provides a decreasing output voltage, one an increasing output voltage, and I forget what the third independent one does, but it is either one or the other! The output signal is checked by the ECU and the two original channels are summed to make sure that the sum is always 12v. When the TPS starts to fail, the ECU detects the erroneous reading because the sum of these two channels no longer comes to 12v, which indicates that one or other of the two has malfunctioned. Normally the problem is wear or crud at a particular point on the track causing a high impedence and low output voltage (open circuit) on that track. The ECU responds by closing the throttle, but as soon as the defect has been passed the normal setting is restored, hence the momentary loss of power. As Diesel Jim says, the symptoms you describe match perfectly the effect if the high/low switch is stuck leading the ECU to operate in low-range mode, when larger pedal movements are translated into smaller throttle responses than in high range. |
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17th Apr 2013 3:46pm |
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| tazmarkuk Member Since: 24 Jan 2012 Location: Birmingham Posts: 134  
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Hi-low range switch? I thought this was a mechanical operation, mine does not have TC, but I will still have look; as the transfer box was rebuilt a few weeks back, thanks for the info
Mark |
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17th Apr 2013 3:48pm |
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| tazmarkuk Member Since: 24 Jan 2012 Location: Birmingham Posts: 134
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Thanks blackwolf that makes more sense now
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17th Apr 2013 3:53pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17218
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Yes, selecting High or Low ranges is a mechanical operation carried out with the lever, and the switch is there solely to let the ECU know which range your using so that it can reduce the sensitivity of the accelerator pedal in low range. It sounds as though yours desensitised all the time. PS - not sure about a Nanocom, but Faultmate allows you to read the inputs to the ECU and will show you whether the ECU thinks you're in low or high. If Nanocom can do the same, and you have one,, it will provide a quick answer. PPS - if it was the TPS, then again there should be faults logged in the ECU. If there are many TPS faults in rapid succession, the MIL will illuminate the the ECU will enter "limp-home" mode. You can reset it with an engine stop/ restart cycle. When my Disco was plying up, if I jiggled the pedal rapidly it made the MIL come on. It really doesn't sound like TPS in your case. |
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17th Apr 2013 4:18pm |
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| diesel_jim Member Since: 13 Oct 2008 Location: hiding Posts: 6074
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Nanocom (even the early Mk.1 version that i've got) will tell you whether the hi-lo switch is on or off.
However, on the early Nano's, it reads it back to front! so it'll say "open" when you're in low range and it should be "closed", but either way, plug it in and change from low to high, it should change the status of the switch. |
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17th Apr 2013 5:11pm |
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| tazmarkuk Member Since: 24 Jan 2012 Location: Birmingham Posts: 134
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Thanks diesel jim, will try this out tomorrow evening
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17th Apr 2013 5:21pm |
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| Bev Member Since: 03 Apr 2013 Location: Perthshire Posts: 267  
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Interested to see what difference this make. When I got my 90 two weeks ago noticed that the diff lock light was not working. Have since fixed the switch, basically a wire was broken of the top and can't say I've noticed any difference in the running. I have nothing to compare to though as this is my first Defender.
It does produce loads of black smoke under hard acceleration though..I believe that has reduced somewhat since fixing the switch.... |
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17th Apr 2013 6:44pm |
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| tazmarkuk Member Since: 24 Jan 2012 Location: Birmingham Posts: 134
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Hi guys, I've just connected the Nanocom and it has logged "gearbox drive open" would just disconnecting and reconnecting the plug sort this or does it require a replacement hi low switch
Mark |
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17th Apr 2013 8:03pm |
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| landy andy Member Since: 15 Feb 2009 Location: Ware, Herts Posts: 5575 
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Think it always tells you that?
But if you go it reading switches you can check the high low switch by going from high to low on the box whilst reading the Nanocom. Andy |
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17th Apr 2013 8:27pm |
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| tazmarkuk Member Since: 24 Jan 2012 Location: Birmingham Posts: 134
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Hi Andy, this was a fault logged, I've also not seen this before. How do you get the Nanocom to read the switch?
Mark |
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18th Apr 2013 7:02am |
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| diesel_jim Member Since: 13 Oct 2008 Location: hiding Posts: 6074
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Go to "Td5 ECU", then "Read switches" scroll along to the "transfer ratio" (they may have changed the name of that one on later version) then when you move the hi-low lever, its status should change. you can also check the clutch pedal switch (on "clutch switch") the "gear switch" one is for auto's only (discovery) |
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18th Apr 2013 7:49am |
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| tazmarkuk Member Since: 24 Jan 2012 Location: Birmingham Posts: 134
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Hi Jim, all done, read switch moved hi low and watched it change on the Nanocom, I'm just about to go out and road test it now. Will post later today the outcome.
When reading faults logged I keep getting temperature circuit current, is this a fault or not as I went to a local Land rover garage who told me this was a fault, they told me it was the temperature gauge switch, this was replace with a new item, not cheap either, but since I've had a Nanocom this has always been the same, so I was wondering was the garage just conning me. Or is the fault some thing else? many thanks Mark |
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18th Apr 2013 9:15am |
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| Porny Site Sponsor Member Since: 31 Aug 2009 Location: Sutton Coldfield - West Midlands Posts: 799 
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I would also have a look at the live data for the MAF (Mass air flow sensor) - it should read 57kghr at idle, and increase to over 600kghr under hard acceleration.
If it doesn't read 57 at idle, it is on the way out. 0 or 4kghr then it is dead. Ian IRB The home of the first modified Keswick Green 90 - and the first 2.4 Puma through both the 200bhp and 550Nm barriers. www.IRBdevelopments.com www.facebook.com/irbdevelopments www.integrated316.com www.facebook.com/integrated316 |
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18th Apr 2013 10:00am |
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