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Car Forum / Saab Cars / April 20079-3 viggen - Throttle Motor. Full PWM in Closing Direction
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? >I get check engine light with two fault codes: 1260 and 1251 after I >took the cylinder head off to change the head gasket. [quoted text clipped - 7 lines] >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. > >I get check engine light with two fault codes: 1260 and 1251 after I > >took the cylinder head off to change the head gasket. [quoted text clipped - 26 lines] > > Colin. The only parts that I disconnected from the throttle body was the limp- home solenoid - I unscrewed it completely since I could not disconnect the connector, 10-pin throttle body connector and two hoses. I left the throttle body bolted to the intake manifold. I will try to wiggle all connectors and maybe apply some electric contact spray. I will also clean the valve itself with the cleaning solution I have from my volvo throttle body procedure... thanks -Peter >The only parts that I disconnected from the throttle body was the limp- >home solenoid - I unscrewed it completely since I could not disconnect [quoted text clipped - 6 lines] >thanks >-Peter One possibility is that something went wrong when you disturbed the limp-home solenoid, and now it's permanently engaged, so the throttle cable is locked to the butterfly. As soon as the ECU tries to set a different position to the pedal, it'll generate errors, and you might be able to feel it through the pedal. Cheers, Colin. > 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? Take a look at the spring on the left side of your throttle assembly, where the cable from the pedal goes in to it. There's a spring there which can be adjusted. lift up the tail on the left /bottom (little tab of spring sticks out), rotate the black plastic assembly in the direction that adds spring tension. Start with one notch. Not sure I can describe the base setting of mine without pictures. > 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? I'd say that since you have the means to read and clear the codes, adjust the mechanical problem that you can, and see if the other code goes away. The throttle assembly isn't too much of a PITA to replace but it's not cheap. The local specialist told me "sometimes resetting it takes care of things" but obviously that doesn't address the root cause of why it jumped a notch in the first place. Let us know what you find, please. More data we have on this beastie the better. Dave Hinz > > I get check engine light with two fault codes: 1260 and 1251 after I > > took the cylinder head off to change the head gasket. [quoted text clipped - 27 lines] > > Dave Hinz I took the electrical connectors apart (limp solenoid, 10pin throttle) sprayed with electrical cleaning spray and put them back and the ride to and from work went without any faults at the cpu. I was very gentle with the car and did not accelerate too much like I did the first time (full throttle to say 100mph). I will try that again on the weekend when I don't need the car to commute to work. Thank you all for comments - I feel like I am learning from you guys! Also, Is there a good description of the Saab throttle body operation? I am kind of lost with butterflies, limp homes, etc. I am interested in the limp home mostly since I may have distrubed it. cheers - Peter >> > I get check engine light with two fault codes: 1260 and 1251 after I >> > took the cylinder head off to change the head gasket. [quoted text clipped - 41 lines] > >cheers - Peter Well basically, it's like this... The cable from the pedal operates the pedal arm. This turns sensors so the ECU knows how much power you want. The ECU then controls the throttle motor which actually opens the throttle disk (the butterfly). The pedal spindle and the throttle spindle should be separate from one-another normally, so with the ignition off, you should be able to move the pedal arm and the throttle spindle won't follow that movement. In limp-home mode, the solenoid does something which locks these two spindles together, so the throttle just follows the pedal position, and the motor can't make any difference. I've just had a look in the manual, and what I didn't realize before is that the throttle body actually latches itself into limp-home mode when the solenoid is triggered, and it needs to be manually re-set. If you just clear the error codes without re-setting limp-home mechanism, "trouble codes P1263 or P1251 will be generated". So, it looks pretty certain that your throttle body is latched into limp-home mode. Here's the procedure to reset it. http://www.stamp.plus.com/temp/Limp_home_reset_1.jpg http://www.stamp.plus.com/temp/Limp_home_reset_2.jpg When you've finished, moving the pedal arm with the ignition off shouldn't cause the throttle spindle to move. Cheers, Colin. >When you've finished, moving the pedal arm with the ignition off >shouldn't cause the throttle spindle to move. > >Cheers, > >Colin. What models/years does this fly by wire architecture apply to? >>When you've finished, moving the pedal arm with the ignition off >>shouldn't cause the throttle spindle to move. [quoted text clipped - 4 lines] > >What models/years does this fly by wire architecture apply to? Not sure. I think it might be a Trionic 7 thing. Cheers, Colin. > >> > I get check engine light with two fault codes: 1260 and 1251 after I > >> > took the cylinder head off to change the head gasket. [quoted text clipped - 75 lines] > > Colin. Great! - I think I was missing the reset. BTW what is the manual that your pictures come from? I reqularly check google and ebay for signs of computer based manuals for saab with no luck. >Great! - I think I was missing the reset. BTW what is the manual that >your pictures come from? I reqularly check google and ebay for signs >of computer based manuals for saab with no luck. Saab call it WIS (Workshop Information System). I bought mine a few years ago from a Saab dealer, but searches for "saab wis" on eBay seem to turn up a few hits. Cheers, Colin. > >Great! - I think I was missing the reset. BTW what is the manual that > >your pictures come from? I reqularly check google and ebay for signs [quoted text clipped - 7 lines] > > Colin. I followed the manual pages you sent and the reset worked fine. The car runs very well now. The reason for all this was that I unscrewed the 'limp home solenoid' triggering it into the limp home mode. I checked with saab WIS on ebay unfortunately all CDs I could find cover newer 9-3 models built after 2003. I need one for 2002 9-3. Anybody seen one like that? thanks again - Colin -Peter |
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