Cami took her ’97 Civic in to get the safety and emissions done last week. Bad news. The mechanic pulled the on-board diagnostic codes (OBDII) and found several things wrong:
P0500 – Vehicle Speed Sensor Malfunction
P1298 – Electrical Load Detector Circuit High Input
P0135 – Oxygen O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)
P0141 – Oxygen O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)
It was looking like we would need to replace both 0xygen sensors, as well as the ELD (Electronic Load Detector) unit. It’s not a new car, but it seemed odd that so many parts would be bad at one time. We have taken our cars to this garage before, and we like their service. But, the total would have been around $450 for parts and labor. I wanted to avoid that if possible, especially knowing the 0xygen sensors would be a piece of cake to replace myself.
As I did some research on the ELD. I ran across a couple of sites that described a similar problem, with the very same trouble codes. One interesting symptom they described was with the Vehicle Speed Sensor. Cami’s speedometer sometimes jumps around like the needle on a polygraph machine. This seemed like the exact same problem. The best part was, it could be fixed without replacing all those parts.
The root cause was a short-circuit between a wiring harness and a metal bracket. The wires are in contact with the bracket, and over time the insulation wears through and causes a short circuit. This causes a fuse to blow, which leads to the trouble codes and erratic behavior in the speedometer. There are some nice pictures on the site. I also found this service bulletin very informative.
This sparked my interest and I wanted to know if Cami’s car looked the same underneath. Night was falling, but the weather was perfect and I was itching to know if this was the cause of the problem. Here are the tools I ended up using:
- Set of car ramps to raise the front of the car
- 12mm socket to remove the two bolts from the metal bracket
- Extensions for my socket wrench. My 10″ extension wasn’t long enough so I either added a 6″ or a 3″ extension to get the length I needed. I can’t remember which one it was, and it was dark at the time.
- Flashlights. I should have used a headlamp, but didn’t think about it. It would have helped a lot!
- Safety goggles to protect from falling debris
- Electrical tape and scissors
- A piece of cardboard to lay on. It makes sliding out from under the car much easier
- Autel MS300 OBDII scanner – $20.44 at Amazon
I shined my flashlight up where I expected to find the blue connector, and sure enough, it was there. The bolts were oxidized, but not as difficult to remove as I thought, especially when I decided to use an extension on the socket wrench.
If I had to do it again, I would use a headlamp and try to find an angle that would allow me the use of both hands. The safety glasses were a big help. Once the bracket was out of the way I could see the wires. They really didn’t seem in bad shape at all, but where the wires had been touching the bracket I could see a rusty mark. I also found an area of damaged insulation on one wire, and possibly another. Using one hand (the other was holding the flashlight) I was able to put electrical tape over the two wires – not easy. I also put electrical tape around the bracket as added protection.
Once I replaced the metal bracket I checked the OBD codes on the new Autel MS300 that was delivered that same day from Amazon. I had ordered it thinking I might need it to check the codes if I replaced the parts myself. As a side note, this little gizmo is awesome! The OBD II plug is just up from the hood latch, under the dash – very easy to access.
The codes were there, just as the mechanic had said. I erased them, which caused the CEL (check engine light) to go off for the first time in many months. But, almost as quickly, it came back on. I had forgotten to check for the blown fuse.
In the driver’s side dash there is a fuse panel and fuse #15 is the fourth from the left, in the middle row.
Sure enough, it was blown.
There was a spare fuse in the panel and when I replaced the fuse and cleared the codes, the CEL stayed off!! Very cool. Now the only thing remaining is to wait for the I/M status to say “Ready”. From my reading it can take several days of driving. I hate waiting. There is plenty of time left to re-do the emissions inspection, but I won’t be totally happy until the whole mess is behind us.
UPDATE:
It took about 6 weeks, but we finally got the “Evap” into a Ready state! That left us with “Cat” and “O2S” remaining in Not Ready. We had enough to pass emissions. Woohoo!
It was a long wait, but at least we didn’t spend the $440 we were quoted to fix parts that didn’t really need replacing. Fixing the short and replacing the fuse was the answer to the Check Engine light. Time took care of the rest.
