Over the last few days my 90 4 Runner has been acting like a dog. So I check the codes and pull a 21 O2 sensor (new NAPA 2 years ago (maybe I need a new one), 43 Starter signal, and a 51 switch signal. While checking the codes I see the ground wire to the fender has come out (so I fix that and reset the ECU) Took for a test drive seems ok for a few minutes and then it starts to slow down again.(no codes this time, didn't run long enough)Help with the code 43, and 51.... Please!!!

 

air filter is always a good blocker of power try that...is it an auto or a manual?

 

It's an auto...

 

Anyone? Come on someone must have another idea!

 

Don't know for sure but here goes... Your probably getting a starter signal code because the wires too it are probably getting a bit corroded by now and the resistance is building up, which is to say the starter is not getting all the juice it needs to give a strong crank to the engine. or else the motor itself is wearing out. the switch signal is probably coming from the starter solinoid switch which may need replacing, (this could also be the source of the starter code, the ecu may be 'double' coding the problem. but these would have nothing to do really with the lose of power to the engine. What you may need to do is get the fuel injection system 'power flushed at a shop. You could try to ut a can of FI cleaner in the tank this may improve things for you, also try to clean/replace the air-filter. hope this helps. Aviator

 

Thanks for the info Aviator. I think I'll just drop the truck off at the shop Thursday night and get the mechanic to look at it... He thinks it may be a plugged cat. I think it may be the TPS...

 

I had a plugged cat too but it did'nt really affect my engine in the way you described I just had less power available Ie had to rev higher to get to highway speed and my MPG sucked. 9opr is that what you were saying was the problem?
Hope it works out for you Aviator

 

Few more threads for you to read.....

For code 43:
https://www.yotatech.com/forums/show...Starter+signal
https://www.yotatech.com/forums/show...Starter+signal

For code 51 (usually a bad TPS)
https://www.yotatech.com/forums/show...+switch+signal
https://www.yotatech.com/forums/show...+switch+signal
https://www.yotatech.com/forums/show...sensor+code+51

For code 21 (not always a bad sensor....can also be broken or damaged wiring too)
https://www.yotatech.com/forums/show...e+21+O2+sensor
https://www.yotatech.com/forums/show...sensor+code+21
https://www.yotatech.com/forums/show...sensor+code+21

 

Thanks for all the replys. It was a badly plugged cat... Was fixed in about 1.5 hours....