'98 Volvo V70R

This is driving me crazy and CEL is on and need to pass emissions. I'd appreciate any advice on what I should look for, etc.

The code refers to a high voltage of the fuel tank pressure sensor. Easiest thing to do is see if there is power to the sensor, I did that, and then replace it, and I did that as well. I don't know if there is a way to test if it is really communicating with the computer. I was really hoping that would work, but no go.

So, am I correct to think that this could also be due to a vapor line or valve from the fuel tank being clogged? That could lead to an actual high pressure reading, right? I went ahead and replaced my purge valve (not the charcoal canister purge valve, but the one near the fan shroud) and pulled two gray/white one way valve in line, and they both allowed me to suck in one direction and not the other.

Since a vapor line goes straight to the charcoal canister, I thought that charcoal canister purge valve might be clogged. So I pulled the charcoal canister and I'm not sure where the purge valve is. I read that it could be of two different types, one is an electrical solenoid purge valve (don't see that anywhere), and the other is vacuum operated and is built into the charcoal canister unit (I think). I pulled my canister out and could freely suck on all holes (that sounds nice), but I don't know if this is correct.

Is there anything else that I could look for? Any other valves or ideas?

Thanks,

Wes L.
Salt Lake City, UT

According to Vadis it maps to EFI-621.. Signal high. If you've verified the supply has power (5V not 12V, pin 3 so left when looking at the pins), have you verified 0 Ohm resistance on the ground (middle pin)?

Diagnostic trouble code (DTC) information EFI-621

Condition

Diagnostic trouble code (DTC) EFI-621 (Fuel tank pressure sensor, signal) is stored if the engine control module (ECM) receives a signal from the tank pressure sensor corresponding to a pressure above 2.95 kPa (signal high) or below -2.88 kPa (signal low).


Substitute value
-leakage diagnostic is disabled.


Possible source

Signal too high
-short-circuit to supply voltage in signal cable
-open-circuit in signal cable or ground lead
-contact resistance in terminals
-defective fuel tank pressure sensor.
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If you're not driving it "like its stolen," are you really driving?

You stated that:

Diagnostic trouble code (DTC) EFI-621 (Fuel tank pressure sensor, signal) is stored if the engine control module (ECM) receives a signal from the tank pressure sensor corresponding to a pressure above 2.95 kPa (signal high) or below -2.88 kPa (signal low).

So does that mean that it could be due to a 'low' sensor to the tank due to a big leak in a hose? Looking at all the hoses in my V70, so many of them seem to be deteriorating, that I could believe that.

Wes

low pressure sets a different code. Low would be P0452, a crazy signal would show up as p0450. They all translate to the same volvo code, EFI-621 (though if you scan with volvo it'll say signal high/low/sporadic).

Make sure you're getting 5V and not 12V on the signal line too.
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If you're not driving it "like its stolen," are you really driving?

I checked again today and no 5V reading. So apparently no power, so what to do?

Wes

Thanks, I'll verify the 0 Ohm resistance on the ground (middle pin) like you suggested.

Wes

Strangely the code does not appear on the MVS list of codes that map to volvo codes. The actual Volvo code may prove valuable in this case, since it seems you've tried the 'easy' stuff.

As you can see on the linked page the P0444 and P0445 both map to the same Volvo code. Sometimes it works the other way around with one P code mapping to more than one Volvo code. Either way, you need someone to tell you what that P code really maps to.

The same smoke machines that can be used on intake and exhaust can also be used on evap systems - maybe it's time to track down a shop that's good with their smoke tester. Or build your own.

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1998 V70 AWD->FWD Turbo 200k+

http://www.obd-codes.com/p0453

this might help