98 v70 NA P0455 - my most loyal friend

[98v70dad]

I bought a Commercial Electric digital multi-meter last night at home depot for $39. Its autoranging, does everything most people would need, has a good backlight AND a little LED flashlight built in. I'm pretty happy with it since it is a nice tool for the price. The $49 Klein with a few more features is also nice (nicer) but I decided not to spend more on something I don't use much.

I'll have some time next Monday to troubleshoot the suspected wire. I honestly really don't know how I'm going to do this. My plan is to disconnect the battery and measure resistance between the negative pole of the connector and something well grounded in the engine bay like the big steel frame on the power steering pump. Unfortunately the other end of the wire in question isn't easily accessible or I would just measure resistance between one end of the wire and the other.

[kahl]

Got the code back after changing out the two hoses in the rear. I found the hose leading from the charcoal box in the left front fender was cracked at the vent valve and the charcoal filter box. Had to drill out rivets and the 3 fender skirt nuts to pull back the fender liner to get to the vent valve.

[98v70dad]

Pretty close to giving up on this one. I am sick of working on it and the thread is long so people have stopped commenting. I guess I can always take it to a mechanic. I'm afraid I don't know how to measure resistance in a wire when I don't have access to both ends without poking holes in the insulation. Poking holes in the insulation is a bad idea. I'm getting 6 to 8.5 volts (plus to minus) at the purge valve connector when I measure it. When I measure the voltage between the positive wire and ground I get about the same as between the battery terminals, 13.6 volts. I think it should be 12V (or thereabouts) or 0V. I know nothing about electrical..asked for help and really didn't get much. The two wires at the purge valve go into a bigger wire bundle which disappears into a much bigger wire bundle near the ECU.

Anyhow, today I cut out a short section of wire that seemed to be limp (partially broken) about an inch from the purge valve and put on a crimp splice and there has been no improvement. I also took out both ECU boxes and cleaned all the connections with contact cleaner. I also reached up on top of the charcoal canister to make sure all of the hoses are still connected ... they are. Nothing else to report ... still stuck.

[rspi]

Found a major leak on a '98 V70 XC today. Hose tore open just below the blue filter near the purge valve. Hopefully that will do it.

[abscate]

Ok dad, let's see if you can nail this.

Switch car off

Pull the plug off the purge valve.
Voltmeter in ohms mode
Measure resistance of each prong of connector to a good engine ground or battery negative terminal. Report back. One of them should definitely be near 0 ohms

I'm not sure how you you can ensure the ECU is sending the full 12 Volts to the purge valve. I think this happens above 1500 rpm but I'm not sure on this. 6-8 volts might be correct for purge valve closed. I'll measure my ME7 today at idle and see if that is useful information

[sleddriver]

Pretty close to giving up on this one. I am sick of working on it

I do indeed understand your frustration. Been there. Experienced that. Have you had time to read the links I posted earlier, detailing the process I went through? Have you built yourself a smoker?

EVAP System Operation & System Diagram


P0455 plagued me for years, before I finally extinguished it for good.

[98v70dad]

Ok dad, let's see if you can nail this.

Switch car off

Pull the plug off the purge valve.
Voltmeter in ohms mode
Measure resistance of each prong of connector to a good engine ground or battery negative terminal. Report back. One of them should definitely be near 0 ohms

I'm not sure how you you can ensure the ECU is sending the full 12 Volts to the purge valve. I think this happens above 1500 rpm but I'm not sure on this. 6-8 volts might be correct for purge valve closed. I'll measure my ME7 today at idle and see if that is useful information

OK. I did this. Measured R for both prongs. I get zero for one of them (blue/green wire) and 370 Ohms for the other (green/orange wire) when grounded at the steel frame on the power steering pump or the aluminum intake manifold. I got essentially the same reading at both of the ground locations I chose (plus or minus a couple of Ohms). When grounded on the negative battery terminal I got 0 Ohms for both prongs. Because it was about to rain I didn't unhook the battery. I'll repeat the measurements when I get more time if it matters much. I know that resistance measurements are more accurate when there is no voltage present.

There is some corrosion in the engine bay on the passengers side because my daughter overheated the car a few years ago and sprayed the forward passenger side with coolant. I did my best to clean it up within a few days of it happening. If the circuit in question is grounded in that area I'm not surprised if the ground is poor. I've looked for the ground location but haven't been able to find it.

[98v70dad]

Pretty close to giving up on this one. I am sick of working on it

I do indeed understand your frustration. Been there. Experienced that. Have you had time to read the links I posted earlier, detailing the process I went through? Have you built yourself a smoker?

EVAP System Operation & System Diagram


P0455 plagued me for years, before I finally extinguished it for good.

If pursuing the possibility of a bad wire or poor ground doesn't pan out I will make a smoker and see what comes of that. I have read the information you posted and appreciate it. I have read posts from many others also. Not one of the rubber items I've replaced looked bad when I took it off and inspected it. So even though there are a couple of rubber items on top of the fuel tank that haven't been replaced I believe that the likelihood of them being bad is low. Building the smoker will be a pretty easy way to confirm that. The fuel pressure sensor could be bad but I know no way to troubleshoot that.

[abscate]

Well I totally blew this. If your 98 is like the 99, the purge should have 12 VDC on the GR OR wire, and the ECU grounds the BL GR wire to open the purge valve.

So ignition on, the GR OR should have battery voltage on the connector prong. If it's 8!VDC something is wrong between battery, switch and control relay-purge valve.

Sorry I missed with resistance approach

You should measure voltage on the GROR wire relative to ground ( battery or good engine ground) with key in run position for next step

Can someone post the 1998 purge valve electrical diagram

[98v70dad]

Thanks abscate. No problem with the resistance idea. For me it was easy enough to try. I really appreciate your help. I'll measure the voltages next time it isn't raining here. I work on the V70 in the driveway and I went out this morning to a raging downpour. Bad commute day.

I looked for a circuit diagram online last week and didn't find much. I did find something but I'm not confident that its for my car and its not accessible to me during the day. The schematic in the back of the Haynes manual shows the positive side going to the fuse box and the negative going to ground that is switched on/off by the ECU.

About a month ago I had to remove the fuel pump relay and jumper the fuse box with a paper clip to get home. I actually drove straight to the dealership, bought an new fuel pump relay and installed it in the dealers parking lot. The jumper was in for about 45 minutes while driving. I don't know if this would have damaged anything, but it has me wondering.

I'm really liking my new Commercial Electric multi-meter. Nice unit for $39.00.