manyunk

I have a 94 toyota 4runner 6cylinder 4WD that has a check engine light on. I initially just changed the o2 sensor but later found out that there was an EGR valve fault. I then changed that too. Before I changed the EGR valve, the light would stay on constantly but now the check engine light comes on and off about ever 20-30 miles. It is currently still on now . . . any thoughts or suggestions?

jandk2005

reset your computer by pulling the fuse or disconnecting the battery for a few minutes, should get rid of all the old computer stored codes

manyunk

have tried that already with both installations of new o2 sensor and new EGR valve

Elvota

Have you actually checked the code? Seems like you have as you are narrowing down your problems to EGR and O2, but maybe if you post the code numbers you are getting someone can help further.

manyunk

had the code checked by the mechanic and he told me it was an EGR fault, . . . don't know the specific code but I will call him tomorrow to get the code and post it on here. . . thanks for the input

manyunk

just a quick update, the check engine light went off again? any clue?

midiwall

Having the actual code will help...

dmatter

My check engine light came on last Night. I Coded it to be "If Possible"...

25
26
51

Can you have 3 Different Codes? in one Setting? The Truck is Getting bad Fuel Mileage about 13 MPG and the Exhaust is in Pretty bad Shape. Any Ideas???

I Changed the Air Filter This Morning and Reset the Light.

regularguy412

Yes. You can have multiple codes. It is 'possible' that some codes are 'old',, that is - they weren't cleared out after a previous problem was repaired ( or not repaired).
Here are the codes and their sources:

25
AIR/FUEL RATIO LEAN INDICATOR--LEAN SIGNAL SENT TO ECU FROM O2 SENSOR

--INJECTOR FAULT(S)

--FUEL PRESSURE

--OXYGEN SENSOR

--AIRFLOW METER OR MAP SENSOR

--IGNITION

--ECU
____________________________________
26
AIR/FUEL RATIO RICH INDICATOR

--SAME AS ABOVE

--COLD START INJECTOR
_________________________________________
51
SWITCH SIGNALS

IDL (tps) CONTACTS OFF, NEUTRAL START SWITCH OFF, A/C SWITCH "ON" SIGNAL TO ECU

WITH DIAGNOSTIC CHECK CONNECTOR SHORTED

--A/C SWITCH/CIRCUIT

--A/C AMPLIFIER

--TPS/CIRCUIT

--NEUTRAL START SWITCH/CIRCUIT

--ECU

dmatter

Thank You for Your Help Guys! I Think I will Start With Getting the Exhaust Repaired And a New O2 Sensor. Truck Really does Seem to Run Fine other then the Loud Exhaust. I have Drove it almost 300 Miles in 2 Days and it Seems to Run better every Time I Drive it.

Thank you Guys

Dax

dmatter

Oh Yeah! I upped Tire Pressure and Changed the Air Filter. It is looking like the Truck is Getting about 17MPG.

thanks guys

regularguy412

Amazing how these little engines respond to some TLC. Mine is a LOT better after getting everything straightened out.

MIke in AR

BeachAssault

Dmatter- I have just encountered the same 3 codes: 25, 26 & 51 out of the blue at the same time ('89 4 Runner).

I was wondering what you have had to do to get rid of them?

From the descriptions 'regularguy' gave us, it seems like you wouldn't expect to get both 25 & 26 at the same time.

My A/C hasn't worked for years, so 51 has to be something else and I hope it's not the stupid ECU.