So we had a 2017 Nissan Rogue come in with trouble codes P0075, P0078, and P0447. Our customer had just moved to the area and needed to get a smog certificate so she could register the car in the state, and of course would rather not have to look at the check engine light on her newish car.
She had taken the car to a Nissan dealer for the same issue, but they were unable to resolve it. To their credit, they did a great job of documenting their testing and results, and that saved me a lot of time in my diagnosis. I’ll give them credit for “loosening the lid”. They also only billed $99 for the attempt, which is the lowest diagnostic fee I’ve seen in at least 10 years. As it turns out, the dealership was in Iowa. Man, California is expensive compared with Middle America, but then again, it’s nice to not have a “real” winter.
What they found were the three trouble codes, P0075, P0078, and P0447. P0075 sets when the ECM doesn’t see power on the wire coming from the intake valve timing solenoid valve. P0078 & P0447 set for the exact same reason, except for on the exhaust valve timing solenoid valve and EVAP vent valve respectively.
The dealership had found a blown fuse #37 had caused all three codes. The 3 solenoids were all powered by the same fuse, so when the fuse blew, the ECM didn’t see power coming through any of the solenoids.
They replaced the fuse and it didn’t blow again. They documented that they had test driven and wiggle tested to try to induce the fault, but couldn’t. The diagnosis ended in an “unsure of cause”.
Since the owner was able to drive for several days without the fault recurring, I can’t really find any fault with their efforts.
Nissan, Nissan, Nissan. Why would you put a fuse, a user serviceable part, on the underside of a control module, blocked by an air intake tube the requires tools to remove. As if that’s not bad enough, there’s no legend for the fuses, so to find out which fuse is which, you’ll need a service manual. It’s almost as bad as their Z cars, which require removing the battery to get to the fuse box.
So, if you drive a Nissan, be sure to carry a tool kit and service manual.
Finding the short
My favorite method for short finding is using a beeper or light. In this video (sorry about the air saw noise), I use a Fluke meter set to read ohms with the beeper on. In this mode, the meter will make a beeping noise when the resistance is very low.
I have one lead connected to the output side fuse terminal and the other lead connected to ground. Nissan provides diagrams of harness routing, so I followed the harness and manipulated it. I only tug, bend and push on areas that either a) flex, or b) touch the engine or chassis.
In an area that flexes, wire insulation can break and conductors can touch. This can cause short circuits of all types. If the harness runs along a ground, the harness can rub through and cause a short to ground. In areas that flex (like between the firewall and engine), I bend the harness back and forth while listening for a beep. In areas that touch ground, I mash the harness against the metal. It’s a waste of time wiggle testing in areas that don’t flex or are well routed.
The smoking gun
Luckily for me, it was easy to strip the harness because there was only a single layer of electrical tape with only 50% overlap. No sheath, conduit, or any other protection against rub-through. It was also pulled tight against the metal valve cover in an ill-advised routing scheme.
I repaired the wire and then wrapped, installed conduit, and then rewrapped the harness. I also changed the routing so the harness no longer rubbed against the valve cover.
I can’t imagine that this will be the only Nissan Rogue that blows a fuse intermittently. They did a really bad job with both design and assembly with this harness. My guess is there will be a whole bunch more Rogues with similar issues. They may not set the same codes, since whatever wire ends up closest to the valve cover will be the one to rub through, but if you are struggling with t Rogue that just keeps blowing fuses, check near the back side of the valve cover.