LH swap high idle

Ok, just finished a kjet to lh2.4 swap with a buddy on a 240 and now we are having the high idle issue after highway pulls. I know the ECU (pin 34) needs a VSS signal from the lh cluster. My problem is after installing the lh cluster everything works except for the speedometer. So no vss signal to the ecu. I carefully compared the 3 pin plug on the back of the speedometer with my plug (lh car) and saw the order of the wiring were different. After switch the order still nothing. I have thought about the different tone ring in the differential. Is it possible to use something like a Dakota digital box to solve this? Rear end signal to Dakota digital to LH cluster??

A car that originally had Kjet wouldn't have a tone ring on the diff for VSS signal, they used a cable off the trans for speedo drive. I think you're going to have to come up with a speedo drive off the trans that produces a digital signal. I seem to remember reading a thread about this, get your search on. Maybe someone with first hand knowledge will chime in here, I only mess with LH2.4 cars.

The cluster gets it's signal stock from the rear end speed sensor attached to the differential in the stock LH 2.4 cars. Either swap that that rear end or put that diff in your rear with that cover that has the sensor or get speed signal from somewhere else. Driveline or front motor pulley perhaps. OR front wheel.... Options aren't endless, they depend on getting it from something turning with car speed....

shoestring said:

A car that originally had Kjet wouldn't have a tone ring on the diff for VSS signal, they used a cable off the trans for speedo drive. I think you're going to have to come up with a speedo drive off the trans that produces a digital signal. I seem to remember reading a thread about this, get your search on. Maybe someone with first hand knowledge will chime in here, I only mess with LH2.4 cars.

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Hi! I?m currently in Taiwan and the 240s here aren?t like what we have in the states. The 240s here are kjet all the way up to 1991 and go straight to a lh2.4 in 1992. My friend?s car was a kjet (1989) but it had a electronic speedo like my 1992. It has a speed sensor on the diff cover. But for some reason my working cluster pulled straight outta my car won?t work in his, this I thought about the possibility of different tone ring.

The wiring in the back of the cluster for the speedo changed at one point. This could be your problem.

I had to swap some wires around for the speedo to work with my setup.

The electronic speedometer needs to be matched to the differential and sensor. In the US, the pre-ABS (antilock braking) LH2.4 cars used a 12-tooth differential, and the ABS cars used a 48-tooth differential. There's a number on the bottom of the speedo, e.g. K9800, which is the expected number of pulses per mile. For ABS cars, it's 4x or K39200. You'll have something similar and can check it roughly by looking up the number of revs per mile or km for your tire size, and multiplying by 12 or 48.

Is your speedo working at all? Where did it come from, and where did the differential come from? If your speedo works, but you have high idle, you may need to run a VSS wire from the speedo to LH2.4 ECU. You can find the VSS signal on the back of the cluster - it's the 2 spade connectors just to the left of the speedo (often with a piece of hose around them to prevent misconnection).

There are a couple nice speedometer writeups on cleanflametrap.com

bobxyz said:

The electronic speedometer needs to be matched to the differential and sensor. In the US, the pre-ABS (antilock braking) LH2.4 cars used a 12-tooth differential, and the ABS cars used a 48-tooth differential. There's a number on the bottom of the speedo, e.g. K9800, which is the expected number of pulses per mile. For ABS cars, it's 4x or K39200. You'll have something similar and can check it roughly by looking up the number of revs per mile or km for your tire size, and multiplying by 12 or 48.

Is your speedo working at all? Where did it come from, and where did the differential come from? If your speedo works, but you have high idle, you may need to run a VSS wire from the speedo to LH2.4 ECU. You can find the VSS signal on the back of the cluster - it's the 2 spade connectors just to the left of the speedo (often with a piece of hose around them to prevent misconnection).

There are a couple nice speedometer writeups on cleanflametrap.com

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Thank you for the reply! The k number on the original cluster is K6241 and the LH cluster is K24964, both are none ABS. I did notice the 3 pin speedo plug had different order but after switching them still no movement from the Speedo.

1) Do you still have the original differential and original differential VSS sensor installed in the car?

If so, I'd swap back to the original cluster, and swap the 3-pin speedo wires back too. This should get the speedo working again.


When you converted to LH2.4, there's a rectangular white 3x4 pin connector that comes off the LH2.4 engine harness where it splits into ECU/EZK cables. The 3x4 connector connects to the cabin&dashboard harness, probably with some custom wiring. The VSS signal to the ECU is the blue/black wire in the 3x4 connector. (You might have a 3x3 connector instead?)

2) Where is the blue/black wire on the 3x4 plug connected to in your car?

When using the original cluster, you'll probably need to run a separate wire to the cluster for the VSS signal. You can find the VSS signal on the back of the cluster - it's the 2 spade connectors just to the left of the speedo, and is labeled with a red "200" in the greenbook drawings. This should be connected to the blue/black wire in the 3x4 connector.