I just bought a beautiful 1991 Lexus LS 400. There are a number of items that I need to get fixed, the first of which is the Cruise Control. When I turn it on the light on the dash comes on. When i try to engage a speed the light goes off for a moment, then flashes back on and finally turns off. all the fuses seem fine as far as I can tell because so many other things are associated with all the fuses that control the curise. Any suggestions as to where i should start? I can get a cruise ECU from Ebay, should i start there, and if so can anyone tell me where this ECU is located? Thanks

Woozy

 

why dont you go check the cruise control actuator first and make sure it isnt broken

 

The cruise control ECU is located behind the lower panel on drivers side. It's a black box about 4"x4" and it should say Cruise control ECU. The problem might not be the ECU. Before just changing the ECU you could do a diagnostic check on the system. http://www.lexls.com/tutorials/intro/codereading.html Using this method with the "cruise" light instead of the "engine" light. Use terminals Tc and E1. Steady blinking is normal. If you get any codes list them here and we can figure what they mean. I have the '93 manual but I think it's the same as '91. Hope that helps.

 

First what would I look for in the actuator that may be broken?

on the post about the ODB I you said to put the jumper on the Tc and E1 terminals, but in the write up it said that those terminals were for air bags, ABS and TRAC, would I still use them for the cruise? So im guessing because my cruise light blinks after i try to set it that it means that there are codes stored?

Thanks

 

To read the ODB I codes it says to be in "N" , the only way to do that is to leave the car in the ACC key position, is that correct? Also it seems pretty hard to get a wire into the ODB holes, i guess i should try to get a solid wire, or in the write up it says something about a "Check Connector" in the engine bay, where would that be? I looked in the fuse box cover but did not see anything except the fuse puller...

 

Yes you Use terminals Tc and E1 for the cruise also. When he mentions the check connector in the engine bay he is referring to using the diagnosis box on the engine instead of the box under the dash. (It's easier) If the light continually blinks every .25 second then it's saying that it is normal, no codes. If there is a pause between the blinks then that's the code number. I use a solid wire and have the car in park when I check mine.

 

Hey Deanshark,

So its cool to have the car in "P" to check the cruise, thats great. Also where is the Check Connector in engine compartment, it would be alos easier than the one under the dash. Is it a standard ODB I connector? Thanks

 

Located on the engine between the oil cap and the intake manifold. Black box says "diagnosis". On the inside of the cover is the label for the terminals.

 

Yeah!!.. I got the new struts for my hood, and they work great, so I was able to get to the Diag box in the hood to check the Cruise Error codes, and it shows a code 13... so now what does that mean??

 

Open in actuator motor circuit
Position sensor detects abnormal voltage
Position sensor signal value does not change when the motor operates

As PureDrifter said, check the actuator. It could also be a bad connection between the actuator and the ECU. Check to make sure everything is plugged in good on the ECU, it's pretty easy to kick the wires while your driving. I don't think it would be the ECU but that's just my .02.

 

According to alldatadiy.com
*) Open in actuator motor circuit
*) Position sensor detects abnormal voltage
*) Position sensor signal value does not change when the motor operates

Thats all the information I found. Looks like I posted the same information as deanshark. I would follow his advice. Below you have a system circuit schematic that may help:

 

OK, so first i should check all the connections from the ECU to the actuator. If all those look good, should i replace the actuator? I cant imagine that a wire somewhere between the actuator and the ECU has broken, if i replace the actuator, with no fix, should i then replace the ECU? Again thanks for all ur help. Im slowly getting my LS in shape. I will be getting a replacement climate control unit, so that should be fixed.. and if I get the cruise done.. all I have left is the tilt and the Auto Down for the power window. I, going to post the P/W question in the forum to see what that looks like

 

That is the order to go in but I think, THINK, if it is reading the code then the ECU would be good, but not sure. If you're decent with a multi meter, the manual shows what every plug and wire is supposed to read, and in what order to check them. It might be cheaper for ya that way, Idk how much those parts cost. Your choice.

 

My cruise doesn't work either...perhaps the guy who fixed the trunk release button in the driver side may have knocked the wire from the ECU...I will check it and let you know if I've fixed the problem...

 

It is located right next to the trunk release cable. Here's a link to remove it and part number. http://www.lexls.com/tutorials/elect...ontrolECU.html