Advanced Engine Diagnostics help

[EYY]

Charge voltage is load dependent. The alternator is independent to the engine management system and cannot be altered. The only thing you can do is make sure that the load sensing wire (white wire) is in good condition that goes to the battery and make sure all earths are good, including pcm earths. Look at a wiring diagram for the VR PCM to determine your earth wiring.

Plug your computer back into the car, turn all lights on, heater fan on full, wipers on etc and check the voltage. If it drops below 12.6-12.8 with that load then I'd be concerned.

The first thing i'd be doing is looking at that o2 sensor issue.

 

[losh1971]

Can I ask EYY what is a cross count on the O2?

 

[losh1971]

I will check the sensor wire. I thought the alt voltage was run through the PCM like a lot of other cars. In the past I have increased the voltage by installing a resistor in the battery sensor.

 

[losh1971]

I want to install some new engine and body grounds as someone has obviously had issues since there is a big red cable coming from the strut nut and onto the engine. Then there is a thinner wire from the battery to the body.

 

[EYY]

No, they only have an injector voltage monitor. This means that if the pcm detects a lower voltage, it'll adjust to hold the injectors open slightly longer to compensate for this.

Adding a resistor means that the alternator thinks the battery needs more charge - and that will work in the same way for your car. But that'd be a last resort.

 

[losh1971]

Voltage only drops to 12.8 if I turn everything on inc the wipers. Turn the wipers off and even with the amp running, hi beams and HID driving lights on it ticks over at 13.3v thereabouts.

 

[losh1971]

I keep getting this and don't know why?

 

[losh1971]

The O2 sensor is not causing excess fuel consumption getting about average fuel usage 12lph. But having said that the issue is annoying and I do want to have it fixed.

 

[EYY]

I'm guessing you're taking those voltage readings at idle. That's fine - nothing wrong with that. Only really an issue when it drops below the battery voltage with accessories etc.

If the O2 sensor really is giving no reading, even intermittently, it WILL be causing excess fuel consumption. Without o2 sensor feedback the computer won't go into closed loop and will give excess fuel to avoid pre ignition or lean running.

 

[losh1971]

Yeah O2 is definitely giving 0 on cross count Getting no fluctuation on cross count at all. Even with driving at 100kph.