2007 Chevrolet Monte Carlo SS Emissions 1 Fuse Blows

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This 2007 Chevrolet Monte Carlo SS came in with multiple complaints including the Emissions 1 fuse blowing in the underhood fuse box. Also there were several codes being set in the PCM as a result, P0030, P0036, P0053, P0054 and P0443. All can be related back to the blown Emissions 1 fuse.

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Because the Emissions 1 fuse was central to all of the codes I started examining the wiring around both oxygen sensors and the canister purge valve. The wire color involved is pink with a black stripe. Those of you familiar with chasing ignition related shorts on GM vehicles are well versed in the pink/black wires. Always looking for them. Both oxygen sensors had been replaced as well as the canister purge solenoid. The wiring around the O2 sensors looked good and so did the wiring at the canister purge solenoid. Following the wiring harness back from the canister purge solenoid around the top of the engine revealed nothing until I moved the harness a little bit near the alternator. I had left the ignition on and had also replaced the blown fuse. When I moved the harness I saw a flash of light from the front driver’s corner of the engine. A closer look showed some discoloration on one of the upper intake bolt heads.

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Looking at the harness from the underside with a mirror and I could see the arc marks in the wiring.

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One thing that was a little surprising to me was how rigid the harness had become from engine heat. I already knew the split loom that is supposed to be covering the harness had already crumbled away from a combination of heat degradation and movement.

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I separated out the pink.black wire so that it could be protected from shorting out again.

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I wrapped the damaged wire and then continued on wrapping the entire harness in the area where the short was found. In most cases I would have wrapped the damaged wire with live rubber tape but given the heat evidence I decided to use a cloth friction tape instead.

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I then wrapped the area with plastic electrical tape to better hold the repair together. The adhesive on the friction tape is not that strong initially but it tends to bond together well over time.

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I proceeded to remove bits of the remaining split loom from around the top and rear of the engine.

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I cut the tape with a razor blade and pulled the reaming pieces of loom out with my fingers and needle nosed pliers.

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I slid the new split loom into position inside the taped areas and then re wrapped the areas with fresh tape.

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I save various sizes of electrical tape rolls. I use the new rolls in open areas and as they get smaller I set them aside for use later in tight areas. Sometimes I might have ten or mores rolls of tape of all different sizes in the top of my tool box.

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In most areas when wires have to be fed sideways out of the loom the factory longitudinal split can be used. In this spot there wire to lead outs on opposite sides of the harness so I had to cut the loom  and notch it to accommodate one of them. It can all be re secured with electrical tape later.

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You can see the spots where I used tape to secure the ends of the split loom and the area where I had to make room for two lead outs of the main harness.

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The customer wanted me to replace all of the missing/damaged split loom in the engine compartment while I had the car in the shop. That was quite a job but it all turned out well. In the next picture the harness looks close to the exhaust heat shield but it is an illusion. In reality there are several inches between the two. As an extra measure against the harness ever shorting out in the original area, I cut a short piece of rubber hose and installed it over the bolt head.

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This Monte Carlo had both oxygen sensors and the canister purge solenoid assembly replaced. None of which needed to be.  Another reason to stop guessing and start testing.

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