What is a G-Sensor?

I've got the check engine light on in my truck. I scanned it and came up with the DTC p1391 and p1393. It's telling me I have "p1391 - G-Acceleration (Low G) Sensor Performance" and "p1393 - Rough Road G-Sensor Circuit High Input".

Can anyone tell me what a "G-Sensor" is?

I would appreciate the help.

Give me your year and I will look it up for you.I believe it sences when you are boucing around( off roading) and adjust timing and fuel trim.Carl

I've got a '97. I haven't noticed it running any different. When the CE light first came on it was only on every once in a while, now, even if I clear it, it stays on all the time.

Thanks,
Jason

I couldn,t find a definition for what it does.After I thought about it I am going to change my answer.It does sence when you are off roading.I think it does this so you will not get a misfire code.While your bouncing around.I don,t believe it canges fuel trim or timing.I don,t work at a dealership anymore and my current manuels do not give a description.But I am pretty sure I am right.I have replace maybe 3 in the last 10 years.Carl

The best location I could find for you is what my manual says.On the right underside of vehicle.You might check the connector.Carl

Do you have any idea where it is located and how much it would cost to replace it? I did get a misfire DTC a while back, but I haven't had it in a while though.

Thanks for all the info.

Jason

Jason,The location I gave is the best I can do,that is all my manuals say.I think it has three wires going to it and sits in a bracket mounted to the frame.I can,t remeber the cost.If you have trouble finding it you might run by the dealer and see what one looks like.If they have one in stock.Carl

Alldata has a service bulletin (SB98-03-L001 JUN 98 DTCs P0101 (MAF)/P1391 (G Sensor) Diagnostics Revised ) on their website (http://www.alldata.com/TSB/29/96290915.html). Might be worth subscribing to see what that is all about.

Here is another link - http://forum.planetisuzoo.com/viewtopic.php?t=177&highlight=p1391&sid=8ce20d5e74febc9a4dd633045ee4f1bd

That's great information guys. At least I know what it is now. Before I had no idea what this thing even did. Now, if I can figure out what it is, then I'll be cooking with gas.

Do you think I can order this thing at AutoZone?

I don't know for sure but my guess is that it is a dealer only item.

Assuming you have found it you might at least check the wires to see if maybe something came unplugged or a looks frayed. If you have a voltmeter you could also check the numbers posted in my previous link. The fact that there is a service bulletin on this makes me wonder if there is some "trick" to the repair. If it was a major problem I would think there would be many, many posters with this problem or even a recall notice. Just speculating so don't put too much faith in this theory.

If it prices out relatively cheap then maybe go ahead and buy it. If it is several hundred bucks, like I noted earlier you may want to subscribe to Alldata. Get the service bulletin first to see if something other than a new part will fix you up.

That's good advice. I'll give a dealer a call and see what they tell me. I have a feeling their going to try to run me through the ringer 'cause I don't know what this thing is, or even where it's at. We'll see I guess.

Thanks,
Jason

it helps to determine the differnce misfire or rough road if memory serves correct
it is locate dbehind the pass rear tire on the inside of the frame rail