Slipping or skipping???
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Slipping or skipping???
2008 Saturn Aura XR V6 170K.
Can't get up hills in 5th without jerky transmission malfunction. All other gears are OK. Can't tell if its missing or slipping but think slipping. Code reads PO300 Random misfire, and P2138 Throttle position sensor correlation off. Am Church Minister with no income.
Can't get up hills in 5th without jerky transmission malfunction. All other gears are OK. Can't tell if its missing or slipping but think slipping. Code reads PO300 Random misfire, and P2138 Throttle position sensor correlation off. Am Church Minister with no income.
Super Moderator
Joined: Jul 2005
Posts: 12,316
From: Slightly off center
Does the check engine light blank all the time or only when you are trying to go uphill in 5th gear?
A blinking service engine light means the engine is actively misfiring. So we need to figure out whether it is misfiring all the time or only under certain conditions.
Anything to do with throttle position is very problematic because basically the car can't figure out how much you are pressing on the accelerator. Your car has one sensor down by the gas pedal and one up by the throttle body itself. I have not looked up the definition of the error, but either they are not saying the same thing or if there is a mismatch and information somewhere else that is going to the computer that doesn't match.
I could, off the top of my head, see the unknown throttle position causing the mix of gas and air going into the cylinders being not always appropriate because the computer is probably using some default value instead of what the engine really needs, giving it either too much gas or Not enough gas, causing a misfire all over the place in multiple cylinders.
I will research the definition of that code later tonight and post back what I find.
A blinking service engine light means the engine is actively misfiring. So we need to figure out whether it is misfiring all the time or only under certain conditions.
Anything to do with throttle position is very problematic because basically the car can't figure out how much you are pressing on the accelerator. Your car has one sensor down by the gas pedal and one up by the throttle body itself. I have not looked up the definition of the error, but either they are not saying the same thing or if there is a mismatch and information somewhere else that is going to the computer that doesn't match.
I could, off the top of my head, see the unknown throttle position causing the mix of gas and air going into the cylinders being not always appropriate because the computer is probably using some default value instead of what the engine really needs, giving it either too much gas or Not enough gas, causing a misfire all over the place in multiple cylinders.
I will research the definition of that code later tonight and post back what I find.
Super Moderator
Joined: Jul 2005
Posts: 12,316
From: Slightly off center
Well, it seems p2138 is indeed related to a discrepancy between the throttle position sensor down by the gas pedal and a comparison of where the throttle plate actually is. If they differ by more than 4% for 1 second, it sets this code.
Most people report that when this code pops up, the accelerator pedal seems unresponsive until about 45% of the way down. This is obviously not right.
Inspect the connector and the terminals it plugs into down by the gas pedal. Also check the wiring for damage.
The overwhelming consensus is that the problem is caused by moisture getting into the underhood electrical center, causing corrosion of terminals and leading to poor connections. The gasket between the top cover and the rest of the box leaves something to be desired and can easily be damaged, allowing moisture to get inside.
Basically, the solution involves disassembling the underhood electrical center and cleaning off any corrosion with electrical contact cleaner.In English, you need to take the fuse box apart with the battery disconnected and hunt for moisture and corrosion. Some claim that the moisture can also get in from the bottom. So you need to take the entire assembly apart to ensure You address all the corrosion and so that you can leave it open to the air overnight to let the moisture dry out.
The majority of people that have done this have said it has solved that code. It is apparently very similar to an issue they have over in the UK with other vehicles derived from the opel line.
I would try this before paying for a new gas pedal/accelerator position sensor part. If it is an issue with moisture in the under hood fuse box, replacing the sensor itself will not help or it will help for 2 days and then the code will come back because it was not the problem.
As for misfires, given that there could be corrosion anywhere inside the fuse box, I would say to try and deal with the fuse box corrosion first and see if the misfire issue is also taken care of.
Most people report that when this code pops up, the accelerator pedal seems unresponsive until about 45% of the way down. This is obviously not right.
Inspect the connector and the terminals it plugs into down by the gas pedal. Also check the wiring for damage.
The overwhelming consensus is that the problem is caused by moisture getting into the underhood electrical center, causing corrosion of terminals and leading to poor connections. The gasket between the top cover and the rest of the box leaves something to be desired and can easily be damaged, allowing moisture to get inside.
Basically, the solution involves disassembling the underhood electrical center and cleaning off any corrosion with electrical contact cleaner.In English, you need to take the fuse box apart with the battery disconnected and hunt for moisture and corrosion. Some claim that the moisture can also get in from the bottom. So you need to take the entire assembly apart to ensure You address all the corrosion and so that you can leave it open to the air overnight to let the moisture dry out.
The majority of people that have done this have said it has solved that code. It is apparently very similar to an issue they have over in the UK with other vehicles derived from the opel line.
I would try this before paying for a new gas pedal/accelerator position sensor part. If it is an issue with moisture in the under hood fuse box, replacing the sensor itself will not help or it will help for 2 days and then the code will come back because it was not the problem.
As for misfires, given that there could be corrosion anywhere inside the fuse box, I would say to try and deal with the fuse box corrosion first and see if the misfire issue is also taken care of.
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