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Old 03-14-2022, 02:02 PM   #2
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Join Date: Sep 2000
Location: Cincinnati, Ohio
Posts: 7,380

1994 SL2
1999 SL
Default Re: 01 SC2 codes, 0302,0405, 1301

Originally Posted by theunpaidBill View Post

So I have an 01 SC2, DOHC, manual transmission that I use as my commuter car. It does roughly 400 miles per week. It's got 277K miles on it, and runs better now than when I got it 4 years ago. Uses about a quart of oil every 4000 miles (I run full synthetic and change it at 6K).

All in all it's a great car.

It's started idling a little rough when it's hot. I changed plugs and plug wires, but the codes came back, so I'm asking for a second opinion on step 2.

Codes are:
P0302 - Misfire cylinder 2
P0405 EGR flow sensor A circuit low input
U1301 Class 2 short to battery

I thought the 0302 would be cured with plugs and wires, as it definitely needed them. My next plan for it is replacing the coil pack. Should I just do the one or hit them both while I'm doing it?

The research around here I see says the 0405 is not unusual for an aftermarket EGR valve because they are not that great. Is my best option to buy one with a warranty and just replace it whenever it starts doing this? Autozone has been solid with warranty replacements.

I don't know about that 3rd one, could it be caused by the EGR issue? I replaced the battery a few months ago and haven't had any problems with it since.
I'll take a stab at your codes. If you have replaced the plugs and wires- did you make sure they were properly gapped at .040?

Also- The Saturn S-Series engine, actually runs better on the NGK Copper plugs then it does on Platinum or Iridium Plugs... If you dig in a bit on the site- you'll see people go either way on them- but the general consensus is that the NGK Copper plugs are better. The Platinum and Iridium plugs run too hot for the S-Series engines.

Here is a thread on the EGR P0405 code. There may be some good info here.

As for the U1301 Code- if you have something plugged into the Cigarette Lighter- it could be causing issues with your electrical system. I would also check with a voltmeter; the voltage you have going on the battery.
With the car sitting- the voltage should read 12 Volts.
With the car running- the voltage should read 13-15 Volts.

With 277K miles on your engine- and if you haven't replaced the coil packs- it is best to replace them together. I would even go to the extent of swapping out the ICM (Ignition Control Module)- which is the "square electrical plate" that the Coil packs are attached to- if it hasn't been replaced before. They are held in with either 8 or 10mm long bolts that attach into the top of the engine block, and can be a bit of a pain, if you have bigger hands, especially since one of the bolts, is partially blocked by the A/C Hose. I once had issues on my 99 SL, where I was getting a misfire code- and it turned out that the coil packs, ICM, Plugs and wires- ALL needed to be replaced.

As a final thought- with that much mileage and you driving 400 miles/week; it may be beneficial to make sure that you have proper compression on the cylinders. The standard for compression should be 180/185-200 PSI across all 4 cylinders. If you have a lower reading on Cylinder 2- then it may be time to think about an engine rebuild, or putting a replacement engine in your car.

Hope this info helps.

94SL2 HCE, "Pearl"

99 SL

94SL2 260K Miles

97SW2 266K Miles

94SC1 340,501 Miles
Org. Engine/Auto Trans
Gone 3/12

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