1999 Volvo S70 T5 - Emissions Fuse Problem

[Pubcha]

I am hoping someone could please help me with an emissions fuse problem I am having. I was given a 1999 Volvo S70 T5 from my father-in-law back in July (2014). When it was given to me, it had the check engine and service lights on. His mechanic said that it was ‘only a broken sensor’ and not to worry about it. I did not worry about it until I moved states and had to go through an emissions test. During the emissions test, the following codes came up:

P0445 – Evaporative Emission Control System Purge Control Valve Circuit Shorted
P0448 – Evaporative Emission Control System Vent Control Circuit Shorted
P0245 – Turbo Wastegate Solenoid A Low
P1332 – Null
P1655 – Null
P0031 – HO2S Heater Control Circuit Low (Bank 1 Sensor 1)
P0037 – HO2S Heater Control Circuit Low (Bank 1 Sensor 2)
P0136 – O2 Sensor Circuit Malfunction (Bank 1 Sensor 2)

I took my car to a Volvo specialist (not a dealership) and they told me that the emissions fuse keeps blowing and that I needed to replace both O2 sensors, with the job costing $950. Searching on forums, I found that the job was not that difficult so I purchased both O2 sensors (I received parts numbers from a dealership to ensure I was purchasing the correct parts) and put them in with a friend that knows more about cars. After we installed them, the emissions fuse kept going out (It goes out immediately when you turn the ignition, you don’t have to start the car). I went to the wiring diagrams and disconnected all parts on the circuit and the fuse was still going out. I disconnected:

7/15 – Front O2 sensor
7/82 – Rear O2 Sensor
8/18 – Canister Purge EVAP Valve
8/19 – Variable Valve Timing Solenoid (Camshaft Reset Valve)
8/28 – Turbo Control Valve
8/44 – EVAP Canister Valve
9/32 – PTC Resistor (Name may not be correct, but component number is)

When all parts were disconnected, I used a multi-meter to check the continuity between the fuse and each component and it tested positive every time. I am not sure what is causing the fuse to blow. I was wondering if I missed a component on the circuit or if I should test the circuits a different way? Or is it something different all together? Any insight would be appreciated. Thank you in advance.

[tryingbe]

You have a short somewhere causing the fuse to blow every time the car is turn on. You going have to find the sort and fix it, it could be a wire that is cut and grounding itself out, it could the insulation of the wire is gone, etc. Look at the wiring diagrams and start at the connectors first.

[Pubcha]

Thanks for the reply! Is there a way to check this with a multi-meter or is a visual inspection the only solution?

[tryingbe]

Multi-meter will only tell you have a short, not much else. you' will have to take the wireloom/tape off to inspect the wires and the connectors.

I would start checking the connectors first, make sure the wires are in good shape and they are not damaged/burnt/cut. If you don't see anything, then work your way up.

[Pubcha]

OK, thanks! I will check the wires tonight. Just to be sure (since I am new at this), does this mean that wires can still have continuity even if they have a short?

[tryingbe]

Open means you won't get continuity.

Shorts means you'll get all the continuity the wire can handle between the 12v and neg ends of the battery. That's why your fuse keep blowing every time you turn the car on. There is a connection made between a 12v wire to either chassis or a ground wire. Find that and you'll be able to get probably most of your issues fixed.

[regent]

Yes, a wire may be shorted and still have continuity from one end to the other.

Visual inspection is the best approach, but you should narrow it down first by separating the parallel branches. There are several branches that feed from the same fuse; you may be able to split them and pinpoint the one that has the offending wire in it and then look for the actual location of the short.

With the prints, locate the pins that feed +12V on the connectors that you have already disconnected, then disconnect the battery, and then read to ground first to confirm that you have a short to ground (you would be reading open or at least several Kilo Ohms if the circuits were OK)