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Life expectancy for Ignition Coils ?

Discussion in 'Gen 2 Prius Technical Discussion' started by PriusGoat, Jul 14, 2011.

  1. PriusGoat

    PriusGoat New Member

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    Just last night I was doing some 100,000 mile maintenance and I couldn't help but wonder what life span the Ignition Coils are suppose to have ? I am all for replacing parts before they "expire" due to the long dreaded drives to Michigan throughout the year.
     
  2. jdenenberg

    jdenenberg EE Professor

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    Mine are fine at 200k miles (2004 Prius). As long as they don't get wet, they should last indefinitely and are not a preventive maintenance item.

    JeffD
     
  3. seilerts

    seilerts Battery Curmudgeon

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    If you did have a failure, it would illuminate the check engine light, but the car is still drivable. The main problem is that it can be difficult to differentiate a failed coil from a failed fuel injector.
     
  4. jdenenberg

    jdenenberg EE Professor

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    I find that it is easy to differentiate the two problems if you can read the codes. Just swap two of the coils and see if the problem moves.

    JeffD
     
  5. PriusGoat

    PriusGoat New Member

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    I did forget to plug in the number 3 coil back in , and received a PO303 error, but nothing a code scanner couldn't fix after I plugged it back properly.
     
  6. Britprius

    Britprius Senior Member

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    Ignition coils are simple devices electrically consisting of two coils of copper wire wound on an iron core. Faults come in three forms,
    (1)Shorted turns between coils (not common).
    (2)Open circuit coils, normally due to poor termination of coil ends (not common).
    (3)Insulation breakdown due mainly to moisture, but can be caused by a loose or badly seated spark plug giving carbon blow bye and burning of insulator making insulation break down the most common and sometimes preventable reason for failure.
    Large spark gaps or fouled plugs will not cause coil overheating but may break down the insulation due to higher unloaded coil voltages, but in the ideal world the coils should be designed with this in mind. I hope this helps with understanding ignition coils.
     
  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    The Prius igniter (aka ignition coil) is more complex than a simple transformer. It includes a power transistor which switches the flow of 12V current to the transformer. Hence, the engine ECU only has to switch each of the four transistors (one for each igniter) on and off in the correct firing order sequence.

    Nevertheless, in response to the OP's question, there is no reason to replace the igniter unless you have a misfire DTC and have determined that the igniter is at fault, or if you see burn marks or rust deposits on the plastic body of the igniter.