2003 Buick Century will start to crank but not start. Also has a po480 code.

chris102576chris102576 Member Posts: 3
edited August 2014 in Buick

We have a 2003 Buick Century that will start to crank and then not turn over. It has a code of PO480 which is causing it to fail emissions and we do not know what to do, dealership was no help


  • chris102576chris102576 Member Posts: 3

    We finally got the car to run and crank, but now the fans aren't working and still getting the PO480 code. Any suggestions would be greatly appreciated.

  • imidazol97imidazol97 Member Posts: 27,104
    edited August 2014

    The code appears to be involving the circuits to the relay and the relay.

    This will involve some electrical troubleshooting on the relay. Look in
    your owner manual and find where it says the low speed fan relay is
    for cooling fans.

    The problem could be in the relay--defective. It could be a fan is defective
    causing the relay to give wrong voltage feedback to the ECU.
    Easiest would be to find the relay. See if the relay has the same part
    number and another relay in the group, such as the horn relay. Switch the
    two. See if the horn doesn't work and the fan does work now.

    You can check the fans themselves for being faulty. That would be my
    second choice of problem. Connect a fused wire from the battery positive
    to the connector for the fan and a ground on the other wire ground. This
    could be dangerous giving a spark or having the fan run. So be prepared
    and be careful. Do it only if you understand how it could work.

    You will need to remove the relay cool fan #3 or disconnect the
    power to the second fan to check both fans in case one is burned
    out or shorted.

    Otherwise you may be troubleshooting a connection in the low power
    circuit to the relay or the circuit from the relay to the fan.

    Here's a circuit diagram with colors.

    The cool fan 1(#12), cool fan 2(#9), cool fan 3(#10) relays are all in the underhood
    relay and fuse box. Check part number on cool fan 1 with the
    horn and other relays to see which two you can switch.

    The circuit is that both fans are in series through relay #1 and that gives
    low fan speed for both fans running because fan #1 grounds through fan #2.
    Then if high AC pressure or engine
    temperature occurs, the fans are switched to parallel power and
    separate grounds by switching the relay #2 and relay #3
    and the fans run at their full speed to cool the radiator faster.

    So the problem with improper voltage could be one of several causes.
    I'm hoping for the KISS method to work and the simplest most likely
    causes to be the problem. But relay #2 could also not be connecting
    to fan #2 to give a ground because of a burned contact or defect.

    2014 Malibu 2LT, 2015 Cruze 2LT,

  • chris102576chris102576 Member Posts: 3

    Thank you so much for your response. I'll repost when we figure this thing out! It's coming up with multiple new codes now so we have someone with a code reader trying to figure it all out now.

  • imidazol97imidazol97 Member Posts: 27,104
    edited August 2014

    @chris102576 said: It's coming up with multiple new codes now so we have someone with a code reader trying to figure it all out now.

    The codes that will pop up will have you chasing your tail if you take each one as an indication of a part to fix. The codes are only an indication of the symptom, so be sure to diagnose before replacing parts based on a trouble code, especially when recommended by a box store employee.

    Now that you see different codes, I'd suggest disconnecting the negative ground at battery and cleaning all the grounds that you see from the battery to various places on the body. Loosen and clean contact. Do same for the positives, especially if your car has positives on top of positives with a lead spacer between. Those can build corrosion and cause grief, as well as they sometimes have deteriorated copper inside the plastic cable from acid deterioration.

    I'd first check the battery for voltage and not having a terminal that's cracked inside the case that gives intermittent breaks. How old is the battery?

    Third would be to consider the computer itself to be suspect. I haven't read of problems but I follow mostly the H-body cars (Bonneville/leSabre and others).

    If you have someone helping you and have a compatible battery, a safe test is to switch batteries with the donor car for a while to see if your symptoms go away.

    A general adage used in a car repair talk show is when strange things start happening in a car, start checking the grounds. But that would include anything that might drop the battery voltage to below 10 v which is when some of the computer systems have trouble operating correctly.

    2014 Malibu 2LT, 2015 Cruze 2LT,

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