Error Codes on ECU

[Nismo_Freak]

I ran the codes on my ECU and I came up with the following:

96 OBDII 240SX

0115 - Fuel System Malfunction (Lean Mixture) 0903 - No Idea 0401 - Air Temp Sensor Error

After reading a bit about MAF sensors and how they work I have came to the conclusion that after no signal from the Air Temp Sensor (it somehow got cut !!? cause it just detached at the wires) the MAF can not calibrate itself to the correct air temp, thus when it is cold the MAF wire is cooled further and it senses larger airflow than is actually passing. Which is why I think the 0115 code is coming up. The ECU is getting a massive airflow signal and it is throwing a code. I've since bumped fuel pressure up a good 6 psi (49 psi @ idle). Am I correct in thinking that the MAF is dependant on the ATS in this manor?

[drjohn]

The int temp sensor is used for diag and has no control over the fuel system or mixture. The hot wire in the airflowmeter cools as more air crosses it and the ecm has to increase the voltage across the hot wire to keep the voltage signal at a certain amount. More air more voltage more air more fuel is needed and thus a richer mixture. This is contrary to your p0115 code which is a lean mixture problem. This could be a vac or air leak or just a leaking exhaust before the cat. which will draw in air and lean out the mixture at speeds above idle. Or just a bad frt. O2 sensor,not enough fuel will cause a lean mixture. The p0903 is a canister vent control valve code and can be caused by a sticking valve or insects stuck in the valve. The valve is located on the can. at the rear of the car. By increasing the fuel pressure you are pushing more fuel through the injectors and causing a rich condition.

[Nismo_Freak]

DRJohn, thanks for the reply ... can you elaborate on the 0903 code for me as how I can fix it? I do have a missing secondary 02 sensor that is causing the 0115 Code. Was I right to push more fuel pressure? What kind of performance loss am I seeing with the codes?

Missing as in... it fell out and got busted up... now it wont go back in. ( Secondary 02 Sensor )

[drjohn]

The vent control valve is bolted to the carbon canister in the rear of the car and is easy to replace. You can check it by taking it off and appling 12 volts to the valve and trying to blow through it. If it leaks replace it. The rear o2 sensor is there to monitor the 3 way cat. converter and has no direct control over engine operation. An int. leak,frt.o2,injectors,mass air flow sensor can cause a lean problem.