XJ XJ12 ( X305 ) 1995 - 1997

X305 TPS setting.

 
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Old 03-04-2019, 10:34 PM
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Default X305 TPS setting.

G'day Gents,

I have a problem with my car, a 1995 X305, in that as I accelerate the car shudders and hesitates.

I have a code reader but no DTCs are displayed.

I had a similar problem a few years ago and it was a dodgy TPS which I had replaced.

As the symptoms are similar to what happened previously I suspected the TPS again and have replaced it with a new one now I'm having a problem setting it up as per the Electrical Diagnostic Manual.

The procedure says to set up 2 DVMs, one to indicate the point at which the IDLE switch opens and the other to measure the mV of the rheostat before and after this IDLE open point and then adjust the TPS until you get a specific difference between the before and after readings.

The book procedure says to make these measurements at the ECM but I found it more convenient to trace the lines through and make the measurements at the TPS, is this a problem?

Being more a nuts and bolts type than an electrically skilled type I am confused. Surely if you have to move the TPS to adjust it then the IDLE open point will also move and when you check it again the readings will be the same. The IDLE switch and rheostat are all part of the TPS and can't moved separately.

Has anyone done a TPS setup on their car and if so how did you do it? Or can you explain how the book procedure works.

Cheers,
Jeff.
 
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Old 03-08-2019, 12:13 PM
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Hey Jeff,

my 96 has the same problem as of recent i took it to Jaguar they have had it for 3 weeks still working on the problem, if u get an answer let m know, otherwise ill get back with you when they figure it out.

reguards , Joe
 
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Old 03-18-2019, 09:45 PM
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I had to put a new TPS in my X305 because the plastic housing was physically worn to the point of being notchy and causing the throttle to stick!

To set the TPS on its slotted mount, I used a DC power supply to put 5V to the TPS input wire. I was then able to set the TPS position to get the right voltage out... I think it was .37? You can get a DC power supply on Amazon. They have like a little digital read out so you can set it to 5v. Point is I did this on the workbench, installed in the car and got no codes . Itís been working perfect
 
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Old 03-20-2019, 05:39 PM
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Hey Jeff,
for my xj12 seems it was the wheel speed sensor left rear causing my engine problem, needed to be cleaned.

reguards , Joe
 
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Old 03-21-2019, 05:23 AM
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G’day Joe,

Thanks for your suggestion but for the life of me I couldn’t figure out how cleaning that wheel speed sensor would make any difference, especially as my speedo was working normally, but it did and my car now runs fine.Thank you.

I’ll have to investigate further to understand why.

Cheers,
Jeff
 

Last edited by watto700; 03-21-2019 at 04:43 PM.
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Old 03-27-2019, 02:00 AM
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That sure is an interesting development! It seems so unlikely, but we have the two of you reporting it. We know that the Left Rear wheel speed sensor feeds the instrument pack and speedometer. The instrument pack also outputs vehicle speed to many modules including the ECM, BPM, ABS/TC module, SLCM, steering module, A/C module, and radio head unit. The ECM also gets vehicle speed information from the TCM. Not to mention, the serial data communication link joins most of these modules too. So it gets complicated. Maybe the ECM was confused by vehicle speed data coming from these sources (like the instrument pack or ABS/TC module) that somehow did not resolve properly.

So Jeff, what exactly happened with your TPS adjustment? Did you figure it out, follow Jagsandmg's procedure, or did you just put the old one back on?
 
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Old 03-27-2019, 09:09 PM
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G'day Richard,

When I removed my TPS I marked the position and installed the replacement in the same position and it seems to work OK. I haven't done any 'hi-tech' adjustment of it yet.

When I removed the LH rear wheel speed sensor there was a large buildup of grease and dirt all over it and the toothed wheel on the axle shaft. I thoroughly cleaned up the lot. The speed sensor though had some surface damage, maybe from a stone thrown up and caught between it and the toothed wheel, so I'll be replacing it.

Cheers,
Jeff.
 
 
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