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Old 05-24-2007, 07:01 PM   #1
Cathyztalkn2u
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Attention P0727 & P1780 DTC's

Ok guys, I am desperate here! I own LS 2000 Saturn, ran fine...then one day would not start. Wait few hours, starts up. no more trouble for a year or so, now is happening on REGULAR basis. Runs when it wants to. Error codes show up as p0727 and p1780...ok, so engine speed input circuit, no signal...uhh, i cannot find a single thing about repairing this in my Saturn Repair Manual..waste of 20 bucks. Please, short of bleeding me dry...anyone out there have any suggestions???

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Old 05-24-2007, 08:13 PM   #2
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2003 L-Series 3.0L Sedan
Default Re: P0727 & P1780 DTC's

DTC P1780 Park/Neutral Position [PNP] Switch Circuit

DTC P0727 Engine Speed Circuit No Signal

1780; The neutral safety switch prevents starting in D, R, and L. Only in Park or Neutral but if the switch becomes misaligned over the years you won't be able to start in unless you push the shifter forward while turning the key to START. Same in Neutral. If a manual then the clutch safety switch may be misaligned.

0727; This one I think is the crank position sensor. Can the starter crank all day until the battery dies w/o the engine firing? The second test is to remove the coil wires from #1 and #4 and crank the engine while observing for sparks jumping across the coils; no sparks = defective crank position sensor. It's located behind and above the starter.

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Old 05-24-2007, 09:36 PM   #3
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Default Re: P0727 & P1780 DTC's

If you have a 3.0L V6, it is most likely a crankshaft position sensor going bad.

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Old 05-26-2007, 03:12 AM   #4
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Default Re: P0727 & P1780 DTC's

Quote:
Originally Posted by CrewCab View Post
If you have a 3.0L V6, it is most likely a crankshaft position sensor going bad.
Yes I do have a 3.0L V6, is there any way of testing to be sure it is the crankshaft position sensor? Stupid car has been dead in driveway for about 9 days now. And yes I can crank it all day and it won't turn over!

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Old 05-26-2007, 06:36 PM   #5
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2003 L-Series 3.0L Sedan
Default Re: P0727 & P1780 DTC's

The easiest way to test the cps is to unplug it and read the resistance of the cps with a multimeter; the resistance should be from 800-1200 ohms. An open or no reading indicates a failed cps. Read this thread; http://www.saturnfans.com/forums/sho...d.php?t=100258 as it covers the cps test with wiring diagrams. Test the yellow and purple wire; an open or failure to read any resistance between the two wires indicates a failed crank position sensor; at $104 - rockauto.com is one place. The third wire is a shield going to ground. The other possibility is the cam position sensor so check the cps first as the cam position sensor can't be tested the same as the cps. The last resort is to tow the car to the Saturn shop for them to determine the fault with their Tech II scanner and they will find the fault quickly.

Because you didn't mention which engine I presumed you had the 2.2L and described the 4 cyl. spark test. The other poster checked his cps by removing one bank of his ignition module and layed it on the engine with plugs connected to test for sparks while cranking. That's a lot of work when its easier to read resistance from the two pins on the cps. Hope this helps.

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