I had been trying to get the cruise control working on my '97 T100. Testing appeared to indicate the ECU was bad. Since I was low on funds and could not find one for under about $150, I put that on hold. Well, I happened across some spare change and found a salvage yard that had two ('97 4Runner and '99 4Runner). They agreed to sell me one for $75. They would not ship it and they are about 100 kilometer (63 miles) away. I hopped in the Prius and drove on down there.

I mounted it, plugged it in and hit the cruise on button. Crap, still broken. I jumped the connectors in the diag port and the cruise light started blinking out a code. Hmmm, 21. That says there is an open in the vehicle speed sensor. Wierd, the ODBII says the ECU is seeing proper vehicle speed.

So I pull the instrument panel out and test the speed sensor on the speedometer. It is making connection 4 times per revolution just like the FSM says it should. OK, put the pannel back in.

Check the code again. I'm a dumb ass that is a 12 not a 21. Problem with the brake switch system. I pulled the brake light switch and tested it with a multimeter. The cruise side of the switch is open no matter what. I took it apart and found 2 broken contact fingers laying in the bottom of the switch body. I soldered them back on, put everything back together and yippy! the cruise control is working.

My fix is temporary. I have ordered a new brake switch.

jrohland

 

Great job on troubleshooting yer situation!

So is yer old cruise control ECU still bad then? Did you try plugging it back in and seeing if it works?

 

I turned that over to my son to tear it apart, and he did. It would be far too much work to try and put it back together.

Based on the previous troubleshooting, I still think it was bad. The CC did nothing with the old ECU. That is, when the switch was pressed, nothing happened as though the ECU was unplugged.

I suspect some previous owner tried to troubleshoot this without the FSM and may have hosed it.

jrohland