Code 25/26

[tsirovy]

My car throws a check engine light and code 25/26 air/fuel ratio lean and rich and cuts off my fuel supply! So I checked and swapped both precat o2 sensors and it makes no difference. I have loud exhaust leak after the cat where it connects to the pipe before the sub o2 sensor and also @ the connection to the Y pipe. After sitting for awhile my car will start, run and drive fine for about 4 city blocks then begin to sputter and die out and not able to restart. I know this maybe should be in the exhaust discussion section but maybe its not an exhaust related problem?

Dont you think if this was o2 sensor related that it would not start up agian after sitting a couple hours?

What do these symptoms indicate the problem could be? I need to figure this out quick so I can drive to work!

 

[tsirovy]

My car no longer throws the code 25/26 instead it brings up 24 after dying. So it is my understanding that my air intake temperature sensor will cut off my fuel supply and regardless shouldnt I be able to bridge B+ and Fp in order to bypass the AITS fuel pump cutoff and keep the vehicle running? I have tried to bridge B+ and Fp after it dies and it will not allow me to restart the car at all! This is confusing

 

[madmont]

Mine will start and run with the air flow meter and air temp sensor unplugged . Does it still run at all? possibly the ecu.

 

[tsirovy]

The engine will start and run not immediately after dying but will start and run after about two or three hours only for a short while again. It does not stay running at all after dying! When I have it running I can unplug the AFM and it will continue to run yes.. but I cannot accelerate at all with it unplugged. Just a side note I was filling my coolant resevoir the other day and accidentally lost my cap, didnt put it back on and drove away. Would the lack of psi buildup cause my engine to die out?? or is it an air intake temp sensor problem causing my engine to die?

 

[tsirovy]

Madmont you may be correct about my ecu! Today again I started the car and it did not run very long at all!! So I checked to see if there was spark and behold I have nothing! So I find it strange that I am able to start the car after waiting some time hours but not directly after it dies. Does this indicate my ecu is going south? Also today I have no check engine light or O/D light when my ignition is in the on position- therefor I cannot check my CEL codes. This has to be the ecu right?

 

[madmont]

Could well be

 

[tsirovy]

Changed my 20amp EFI fuse b/c it was blown so now I have indicator lights and spark. But definitely no fuel. I will have to look into my fuel pump and or fuel filter next.. its all I can think of. But I dont know why it would work intermittently.

 

[tsirovy]

So today I remove my fuel pump from the tank to see if it works- i hook it to a battery and voila it does in fact work!
But just before removal I turn my key to "on/run" and no fuel pump operation... even when B+ and Fp are bridged!
I reinstall the fuel pump as I know it works.. turn the key to on and hear it working b/c the lines were free from fuel.
try to start the car and the engine would not start.. soo i turn the key to on again and no operation of fuel pump even with B+ and Fp bridged?? Ok
Strange so I am led to believe now that I have a completely blocked fuel filter because I have no fuel pressure at the fuel rails. And if I remember correctly the fuel pump will not operate if it believes there enough pressure in the lines.. so this would have to be the fuel filter right? I am stumped

 

[Lextreme]

Fellas, have a customer who did an EGR delete and now three weeks later, he's throwing 25/26. Any insight?

 

[Supra967]

Code 25 is Air fuel ratio Lean malfunction and

Code 26 is Air fuel ratio Rich malfunction.

You should do the o2 sensor check below for these fault codes. Basically if you check the voltage on the o2 sensors and you read 0 or 5 volts you know you have a problem.

I did the test and my voltmeter was pegged at 5 volts. Follow the troubleshooting chart below and it leads right to a lean condition; my fuel pump ECU was not working properly at low speed.

 

[Supra967]

And if you have to replace oxygen sensors, use Denso OEM not cheap junk.