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Ignition coil & air/fuel ratio sensor

avatar2112avatar2112 Member Posts: 1
edited June 2014 in Subaru
Okay, my story is that just yesterday I had my battery (~5 years old) replaced by AAA. They told me I had a dying/dead cell. Immediately afterwards, my check engine light came on. I took it to a local shop, and the dread codes claim I need a new ignition coil (& wires & plugs) as well as a new air/fuel ratio sensor.

My question is threefold:

1) How critical are these systems? My guess is both are critical, I just want to check with the amatexperts.

2) Is ~$670 a decent price for parts and labor for both fixes? That seems a bit on the high side (~430 parts, ~240 labor?)

3) Could either of these have been caused/aggravated by replacing a battery? (i.e. could they have been damaged in the battery install, or would a new battery cause these to fail anyways.) In other words, can I blame this on somebody else?

Any advice is much appreciated, and thanks!


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    xwesxxwesx Member Posts: 16,836
    First, did you notice any "odd" behavior of the car when or after the CEL illuminated?

    I think the best course of action, if you did not notice anything odd, is to write down the codes and reset them in the computer. It may be that there was some sort of electrical hiccup when the replacement occurred. If the codes immediately (or soon) return, there could be a problem with one or more systems. If that is the case, I would start with the coil, wires, and plugs, repeat the process, and then change out the sensor if the code(s) continues to return.

    1. Critical. The first supplies the spark, the second dictates the combustion materials. If either goes awry, you will get poor performance or no performance.

    2. I would estimate about $80 for the coil, $45 for the wires, and between $20 and $45 for the plugs (depending on what you get). I am not sure about the sensor, but $430 versus ~$160 means that is one heck of an expensive sensor. I doubt it is more than $100. Most sensors tend to run between $60 and $100. $240 for labor doesn't seem overly unreasonable depending on the shop rate, but I would estimate about 2 hours for this job. The plugs are a PITA to access.

    3. I tend to think of these things in terms of causality versus coincidence. However, I am more inclined to think that the defective battery would have contributed more to damaged parts than the new one. I don't think there is something that could have happened during the actual installation to have caused a failure (in other words, something you could blame on someone else!); possibly, but I am not conceptualizing the link at this point.
    2018 Subaru Crosstrek, 2014 Audi Q7 TDI, 2013 Subaru Forester, 1969 Chevrolet C20, 1969 Ford Econoline 100, 1976 Ford F250
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    ateixeiraateixeira Member Posts: 72,587
    Critical, agreed.

    With a bad spark you send unburned fuel downstream and then your cat gets clogged up and it costs you far more.

    $80 for a coil, wires vary but get the good ones, not the cheap bargain priced ones.

    It's not too hard to do yourself if you have a ratchet with various lengths of extensions. One of those flexy ones makes the job easier. You can reach up from the bottom, that may be easier then working from the top reaching down (nothing to remove).

    A bad battery would strain the alternator because it would constantly ask for more charge, so I can see how it could be linked.
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    thestickthestick Member Posts: 1
    My check engine light came on for my 2007 camry SE so I took it in to toyota to be checked. I spent $95 for the diagnosis and they said I need af sensor b2s1. They want to charge me $427 for parts and labor. How soon does this need to be done before there is damage to cat conv? Is this something that can be done on my own or is this a reasonable price?
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    ateixeiraateixeira Member Posts: 72,587
    Not sure where that sensor is located. It can be anywhere, even differnet for the I-4 vs. V6 engine. Ask in a Camry forums, perhaps someone will know.
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    xwesxxwesx Member Posts: 16,836
    I agree. Sounds like it is an airflow sensor, which is usually in the air intake system (right on the top of the engine bay, typically easy to access). If this is the case, you can easily do the work yourself with little or no experience. The part may be spendy though. A new mass airflow sensor for my '96 Outback was around $350 back in 2000. :cry:
    2018 Subaru Crosstrek, 2014 Audi Q7 TDI, 2013 Subaru Forester, 1969 Chevrolet C20, 1969 Ford Econoline 100, 1976 Ford F250
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