Date: Wed, 11 Apr 2007 18:18:21 +0100
From: Colin Stamp <col.dustbinnospamp.plus.com>
Subject: Re: 9-3 viggen - Throttle Motor. Full PWM in Closing Direction


On 11 Apr 2007 08:30:34 -0700, "pzi" <pzinospamnet> wrote: >I get check engine light with two fault codes: 1260 and 1251 after I >took the cylinder head off to change the head gasket. >The first one 1260 is the "Throttle Return Spring. Too Low Force" and >the second one 1251 is "Throttle Motor. Full PWM in Closing >Direction". I understand the first one but what is PWM in the >second? >When this happens I feel a bit of rough operation of the accelerator >pedal. I think this may be the accelerator pedal wire dirty or >damaged. Strange is that this does not happen all the time - all >clear for 30 min of driving and then it is. I read the codes and >clear them and its ok for next 30 min. Any other ideas? PWM is "Pulse-Width Modulation". It's the method the ECU uses to control the amount of force the motor applies to open and close the butterfly. Both codes seem to be different levels of the same problem - the ECU is having to drive the motor harder than expected to close the throttle. Full PWM would mean that the ECU has had to turn the motor power up to maximum when trying to close the throttle, and it's still not enough. I don't think it'll be the throttle cable, since that's not involved in actually moving the valve unless the "limp-home" solenoid is engaged. It would have to be something about the throttle body itself, like a sticking butterfly. I would check everything you disturbed around the throttle body. Is it possible that it might not be bolted down flat so it's a bit distorted? Cheers, Colin.

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