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Hey everyone!! I know there are tons of threads on this but they're either hard to find or else what I DO find doesn't work to fix my issue. I've got a 99 LS400 and my speedometer and odometer went out. For the first few weeks of them not working, all I had to do was give it the ole smack on the dash to fix it. Now neither work no matter the smacking but they DO work after I have disconnected and reconnected the battery. That trick only works for the day and they stop working after. I'm wondering if its a possible speed sensor, ECU issue, or worse.... PLEASE HELP
it's uncommon to find an intermittent speedo/odo on newer model LS400s, which are usually attributed to the ECU capacitors that affect early models (90-94 primarily, 95-97 not as much, 98-00 rarely). you could be in that rare category!
percussive maintenance could have been a loose wire, but the disconnecting and reconnecting of the battery points to marginal capacitor performance in the ECU...
Hey everyone!! I know there are tons of threads on this but they're either hard to find or else what I DO find doesn't work to fix my issue. I've got a 99 LS400 and my speedometer and odometer went out. For the first few weeks of them not working, all I had to do was give it the ole smack on the dash to fix it. Now neither work no matter the smacking but they DO work after I have disconnected and reconnected the battery. That trick only works for the day and they stop working after. I'm wondering if its a possible speed sensor, ECU issue, or worse.... PLEASE HELP
The important first step is to know how the speedometer and odometer are driven. See the signal flow below. VVT engine models do not get the speed signal from the transmission. Those get it from the ABS/TRC/VSC computer as is shown below. One tire rotation generates 48 pulses and the pulses are sent and processed by the ABS/TRC/VSC computer and then processed signal sent to both the odometer and speedometer. The process is to remove the noise and to get the average and then divided by 12. So the cluster unit receives 4 pulses when the tire fully rotates 1. I imagine that your ABS/TRC/VSC computer's system reset circuit is not functioning or the cluster unit has some problem.
Ohhhhhh okay! So how do you think or suggest I go about fixing the problem?
Originally Posted by Yamae
The important first step is to know how the speedometer and odometer are driven. See the signal flow below. VVT engine models do not get the speed signal from the transmission. Those get it from the ABS/TRC/VSC computer as is shown below. One tire rotation generates 48 pulses and the pulses are sent and processed by the ABS/TRC/VSC computer and then processed signal sent to both the odometer and speedometer. The process is to remove the noise and to get the average and then divided by 12. So the cluster unit receives 4 pulses when the tire fully rotates 1. I imagine that your ABS/TRC/VSC computer's system reset circuit is not functioning or the cluster unit has some problem.
Ohhhhhh okay! So how do you think or suggest I go about fixing the problem?
What I can suggest is to observe those signals using an oscilloscope professionally. As an EE myself, I'd try to find the exact failing point using an oscilloscope, data analyzer, TDR and others.
Without measuring equipments, it will not be easy to troubleshoot. One simple idea is to replace the ABS/TRC/VSC computer or the cluster unit. Sometimes the signal line is disconnected and in this case it can be fixed rather easily using a multi meter.
99 LS400 Odometer/Speedometer Not Working
