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.

 

Try unplugging the MAF and see if the fuse blows.

I would pull connectors 1 at a time until the fuse stopped blowing. Sounds like there is a short somewhere. Check for frayed wires around the motor. Not fun but there is a short somewhere. You may also try unplugging the ECU and see if it still blows.

 

First, I didn;'t know there was a emissions fuse, but clearly there is some fuse that blows.

Anyway, pull the fuse and find the battery side of the fuse. You will need the 12V DC scale of your meter - one probe on ground, one to each side of the fuse. The positive side will read 12 or more volts.

Make sure you have no voltage on the non-12 volt side of the fuse. Switch the meter to OHMS. One probe on the non-12V side and the other to ground. You should not get a short to ground which will show up as a 1 or something along those lines. Connect the 2 leads together if you don't know what the the meter does.

If you have ALL the sensors disconnected (based on the diagram) you should get infinity or o, depending on the meter.
If you are getting anything other than that you have a short in the wiring. Likely a shaffed wire to ground. You poor connection or something that is shorting the wiring. With a diagram you just follow the wiring from the fuse out to each sensor or other connector. Leave everything disconnected until yo9 ufind it.

Good luck