I have a 99 Civic throwing a bunch of codes. I checked around and found the TSB about the harness rubbing on the intake manifold bracket but when I pulled it apart the bracket was different than pictured and there was no damage to the wires. Checking the TSB closer my VIN doesn't fall into the range they specify. Did some more checking around the O2 sensor and VSS sensor wiring, didn't see any damage. Fuse 15 wasn't blown either. The speedo is intermittent and I'd previously changed the VSS and checked the main relay to no effect. Any suggestions would be highly appreciated. Thanks for reading.

 

Test that power is reaching the yellow-black wires at the oxygen sensors. Test sensor heaters for continuity (10 to 40 ohms).

When the speedometer doesn't work, look to see if the odometer is still rolling normally.

 

I'll try the O2s, thanks. The odo went out with the speedo. However I must have tickled something this morning because the speedo is now steady on the throttle and bounces around when I let off the gas. The motor mounts are probably originals and likely shot so maybe it is a wire getting pulled or rubbed somewhere else. I couldn't get the bracket out as there was forty seven hundred wires and vacuum lines stapled to it and I didn't have too much time to work on the car this morning. But my weekend just started so I can look forward to much more wire chasing. Yay...

 

First test fuse 15:
https://honda-tech.com/forums/honda-...fuses-3079359/

Next, when you reset the ECU, which codes return?

 

Turns out fuse 15 was blown, must have missed that tucked behind some aftermarket power wire running to the fuse next to it. Anyway, replaced it and it popped again immediately. Clear the ECU and the same five codes return immediately as well. Did some more wire tracing, got some long reach pliers to get the bracket out and get a better look at the wiring behind it, still didn't see any damage. Tried ohm testing the forward O2 and couldn't get anything out it of except the two black wires showing 8 ohms. Still have to check for power at the O2 connectors. Something I did find is that whatever monkey welded in the replacement cat the previous owner mentioned did so backwards and the rear O2 sits too far forward and hits the sway bar at some point during accel/deccel. Thinking that might be the cause, I disconnected it and interestingly enough all the same codes came back after clearing the ECU but the fuse didn't blow. Don't know what to make of that, figured it would pop a code for the rear O2 but the others might go away. Might still be a wire damaged somewhere. I have a Honda FSM for it and checked the O2 section but everything requires a scanner to do it their way. It's nice they have an ECU pin out with voltages at different operating modes but I couldn't find a section that said this is the O2, theses wires should give this reading. And I sure hope that damn long runner intake makes a buttload of torque because it sure makes working on the back side of this engine a pain in the *****. /rant

 

Sounds like the hot heater element wire for the primary or secondary O2 sensor has a short.

 

Drive up on ramps and get underneath the car, the harness is easier to reach from there.

 

Problem solved. All of the codes coming back struck me as kind of weird. I had been using the engine bay fuse for the ECU to clear the codes and then the Honda two pin connector to read them. That was all a bit time consuming so I bought a cheapie code reader and cleared them using that. Lo and behold, all the codes went away except for the rear O2. Pulled that out and sure enough there was a heater wire rubbed through where it was hitting the sway bar. I'd already bought some O2s in case I needed them, swapped out the rear and boom, dash is clear. Thanks everyone for the assist.

 

Good job.

Resetting the ECU with the Back Up fuse requires that it be removed for 3-5 minutes.

 

Just pulled the ECU fuse, no wonder it wasn't working.

 

See Codes sticky. The ECU is reset by removing the 7.5A Back Up fuse.