gymguy Posted October 28, 2011 Share Posted October 28, 2011 Fixed most of my LS400 instrument issues (lights, gas gauge, sticking needles) but the speedometer is linearly low on actual speed (error increases as speed increases). I know this because of my GPS. I suspect that the electrolytic caps on the meter board (C2, C3, C4) attached to the needle movement may be the culprit since they are the same age as those that have failed on the lights and gas gauge circuits. I believe this speedometer design uses a hall effect sensor on the transmission that sends pulses to the meter board where a microprocessor counts the pulses and drives a stepper motor attached to the needle. This seems to be the typical design used for analog meters today. Does anyone have a schematic of the meter board or have experience with this problem? Quote Link to comment Share on other sites More sharing options...
landar Posted October 28, 2011 Share Posted October 28, 2011 It is quite 'normal' for the speedo readout to be inaccurate by as much as 3 mph. It usually reads higher than actual but could vary depending upon your tire size. How much inaccuracy are you seeing and to what side (high/low)? Quote Link to comment Share on other sites More sharing options...
gymguy Posted October 30, 2011 Author Share Posted October 30, 2011 It is quite 'normal' for the speedo readout to be inaccurate by as much as 3 mph. It usually reads higher than actual but could vary depending upon your tire size. How much inaccuracy are you seeing and to what side (high/low)? Indicated Speed at 65 MPH is actually 75 according to my GPS. At 55 it is about 64. My tire size has not changed for 5 years. Six months ago the reading was accurate. I have another LS400 (1994) with readings that agree with the GPS. Quote Link to comment Share on other sites More sharing options...
AzHotLS Posted October 30, 2011 Share Posted October 30, 2011 You may have already seen this so I don't know if it'll help but..... http://www.clublexus...sor-issues.html Here's a schematic that lists speed sensor 2: http://www.clublexus.com/forums/ls400/553965-cruise-control-inoperable.html Have you tried the "smack" method: http://www.clublexus.com/forums/ls400/578054-speedometer-shows-wrong-speed.html Quote Link to comment Share on other sites More sharing options...
VBdenny Posted November 8, 2011 Share Posted November 8, 2011 Mine reads off but consistantly 3 mph fast. No variation over the last time I changed tires maybe 40,000 ago. Quote Link to comment Share on other sites More sharing options...
fsuguy Posted November 10, 2011 Share Posted November 10, 2011 I recently had occasion to replace my tach ('92 LS400 & sticky tach issue) and in the process moved my speedometer needle a bit. Now it is off by about 15mph. I have not fixed it yet since I will have to take out the instrument cluster (PITA!! because of the connector plugs, but will do so as soon as I get my replacment cluster indicator bulbs) but I think that it will be simple to fix - there appears to be a sort of stop inside the mechanism to prevent the needle going below zero mph; it looks like if you move the needle manually, it is possible to move back beyond this point resulting in the needle dropping to below the zero mark. I think the fix is to very gently lift the needle and turn it clockwise so that it is in front of the backstop and pointing at zero. The tach fix was similar. HTH Quote Link to comment Share on other sites More sharing options...
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