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PCM/O2 sensor failure relation? 1996 Civic 5-sp/98,000


I’ll try to be concise on a service-related issue, but I could use some feedback.

In early august I noticed an engine malfunction light on my 1996 Honda Civic DX hatchback 5-sp/98,000 . I promptly took it to my Honda dealer which took several hours to diagnose the problem as a bad wiring harness. I was told the vehicle was now fine and I had no light, but I noticed my cruise control no longer worked. I mentioned this to my service manager who mentioned they did nothing. Huh? It was working when I arrived and they changed a wiring harness. Regardless, I was told to take it to the shop that installed the cruise (Honda offered no cruise in '96, but my dealer had it installed 3rd party and I bought the car through this dealer with cruise installed).

The cruise control shop quickly found the problem as a wire which had been worked loose. I returned to my Honda dealer and they agreed to reimburse me. That isn’t my primary problem, but it was a pain and I made three trips instead of one. I consider it relevant to the full story.

About two weeks ago I again noticed the malfunction light. I was less concerned this time and decided to wait a few days to see if it was sporadic. I took it in 09/27/10 after testing it several times and having driven it no more than ten miles after the light appeared. Again, Honda had the car through the day but this time I was told I had a bad PCM and it would cost $760. I wasn’t charged for the diagnosis as their August effort had apparently been for naught.

I waited a few days before authorizing installation 10/01/10. Tuesday (10/05/10), I learned the car was ready. But within five miles of retreiving the car the malfunction light reappeared. I took it in yesterday (10/06/10), and after another full day of diagnosis, I was now told the problem was a faulty oxygen sensor. They offered to replace the sensor with a used unit at no cost and no cost for the work or diagnosis.

OK, I realize things happen on a 14-year-old car, but I’m suspect an oxygen sensor and PCM failed concurrently and independently. Did the failure of one cause the other? And, had the problem been properly diagnosed in August, after I quite promptly took it in, would the PCM have failed? I did drive the car approximately 1,000 miles camping after I was given the thumbs up by Honda.

I asked my service manager about the possible relation. He answered we’d never know but one probably caused the other and the sensor probably caused the PCM to fail. I was surprised by his frankness, but not his thesis.

So my question is whether I’m justified in asking for a reduction in the PCM installation charge? Perhaps installation at cost? I realize they didn’t charge for the PCM or oxygen sensor analysis. However, that work was necessary as their August work was incorrect. And I was charged $170 in August and $767 for the PCM.

Although I’ve made FIVE trips on this problem, I’ve not lost my temper, used poor language, or been unreasonable. I’ve used this dealer since I bought the vehicle and have had no problem. I also don’t consider them to have a bad reputation. Thoughts? Guidance?

Well, I can’t know from here, but…
I think that the most likely thing is that they did incorrect diagnosis each time and that either your one and only problem was the O2 sensor all along, or you have some other problem that still isn’t really fixed and the light will be back on soon.
I really doubt that the PCM needed to be replaced.

Ditto to what Tardis said.

I suggest that for future service and repairs you find a reputable independently owned and operated shop instead of returning to the dealer. They are not doing you any favors. They’re just “doing you”.

Thank you all for replying. I should mention I phoned the dealer as soon as the light appeared the last time to make certain they’d not nuked my old PCM. I strongly suggested they test the old PCM with the new (albeit used) O2 sensor. They agreed to do so but reported the old PCM tested only three volts, 25% of guideline. I struck me as odd, as when they decided it needed to be replaced I was told it registered zero voltage.

Regardless, IF the PCM was bad I consider it uncertain their mis-diagnosis was not responsible. Unfortunately, it’s certain they profited from charged installation labor and their parts markup. It’s also certain both cost me.

So, the mismatch of those two certainties leads me to request an adjustment on the PCM. I’ll do that next week unless someone can direct me otherwise.

An update … This morning (10/10/10) I started my Civic for the first time since retrieving it. Indeed, a solid engine malfunction light as soon as it started. The fun never ends!