8.1L Vortec Loss of Power / Check Engine Light

[azstarr]

UPDATE: Did a quick 200 mile trip this weekend. Used the code scanner to check for codes before I rolled...clean..no codes. Ran 100 miles to Tucson and checked for codes upon arrival..no codes. Before rolling out this morning checked for codes just to be sure...no codes. Ran a 100 miles back home..no check engine light. Thought I was out of the woods...thought the seafoam had done the job. Got home checked for codes....no luck...had one pending code P0151 (bank 2 sensor 1 low voltage). I'm thinking its just a matter of time before I triggered P0131 (bank 1 sensor 1 low voltage) again and then eventually the check engine light again. I think my next move is going to be replacing both O2 sensors..again, I'm thinking the cracked exhaust manifolds may have damaged the sensors. Will also pull the plugs on both banks to see how they are looking...see if we are running lean. Any other suggestions?

I will say the code reader was a great investment for those of you that don't have one. Just knowing that something isn't right...or that all is working fine...is a good feeling. I'm thinking about putting this code reader in my truck and then buying the scangauge II for the RV. For those of you that have this reader, how do you like it?

[DriVer]

Originally Posted by azstarr

I will say the code reader was a great investment for those of you that don't have one. Just knowing that something isn't right...or that all is working fine...is a good feeling. I'm thinking about putting this code reader in my truck and then buying the ScanGauge II for the RV. For those of you that have this reader, how do you like it?

azstarr, Although the code reader that you have will offer insight into what problems might present as an obvious DTC, nothing will replace having the ECM scanned by a Tech II. This would be how I would handle this situation prior to buying the O2 sensors. Make sure 1st and buy on the diagnostic of the Tech II.

[azstarr]

I know I'm showing my ignorance here. Is a "Tech II" the same thing as the scangauge II or is a Tech II a mechanic with this certification? Learning.

[garyspang]

Don The Ham
If your backfire is not very severe, four bottles in a full tank of gas may give you the improvement you need. But if it backfires just before or after an acceleration cycle, then the tool will allow you to shoot 50% TECHRON into the combustion chambers for heavy duty cleaning. It is tricky to use the tool, you need an air compressor and set the tool pressure slightly above the rail pressure. Study the instructions enclosed with the tool.

[DriVer]

Originally Posted by azstarr

I know I'm showing my ignorance here. Is a "Tech II" the same thing as the ScanGauge II or is a Tech II a mechanic with this certification? Learning.

A Tech II is a professional testing instrument and the standard tool that is used at all GM & Workhorse Service Centers to diagnose in depth any issues or problems that may present a diagnostic trouble code (DTC). ScanGauge although a good working consumer based device does not approach the performance that is available form a Tech II.

A Tech II will also run ~$1,000.00 and gets periodic software updates on a subscription basis to keep the diagnostic capabilities up to date. It is always preferable to have a technician with an ASE certification that understands in depth the challenges that may present from modern internal combustion engines...

[azstarr]

ok, thanks....I'll get with the local GM dealer and see if they can do the diagnostic on an RV....closest RV service center is 100 miles..one way...

[DriVer]

Originally Posted by azstarr

ok, thanks....I'll get with the local GM dealer and see if they can do the diagnostic on an RV....closest RV service center is 100 miles..one way...

azstarr, Unless you have a need to have a scan done immediately, you could choose to wait until such time as it is convenient to you. Perhaps you're thinking about camping out that way?

I have a Scan Gauge II, X-Gauge, so yes I do use it all the time however I accept that it's not a Tech II and if I have a major problem there's a Tech II only about 15 miles away.

[Don The Ham]

garyspang

I am heading to Hunting Island State Park in three weeks, I will add Techron on return from this trip and see how it works out. This way I can compare the before and after over the same route. My back fire is under heavy load only.

[azstarr]

Update: Well, finally got a TECH II to check out codes (local GM dealer did it for free). They confirmed what my reader told me, both O2 sensors showing bad; P0151 (bank 2 sensor 1 low voltage) and P0131 (bank 1 sensor 1 low voltage). Tech said that probably when the manifolds cracked the sensors became clogged with carbon. So I replaced the sensors, which was an easy job. Turns out the local NAPA did not have two of the same brand of sensors so I went with one Bosch and one Denso. The OEM was a Denso but the part number has changed from 12572706 to 234-4669. The Bosch part number is 15282. Bosch was more expensive but the sensor has a shield over the holes so supposedly that helps keep the carbon out and it will last longer. Been on a couple of short trips (less than 300 miles) since the install and so far no new codes coming up and she seems to be running fine. I also cleaned the MAS. One other note: I discovered this asbestos wrap that is used to wrap around motorcycle exhaust pipes (right at the head). So I bought a roll of this stuff and wrapped all my plug wires from the boot right up to where they come near the exhaust manifold. Works great.

[rgreen45]

Interesting thread gang.

FTR, in all my years I've never had a bad O2 sensor cause reduced power. The ECM ingores the faulty signal and compensates in other ways. Then again, I've never had a WCC with a faulty O2 sensor.

Almost any other mechanical/electrical issue can cause a fault in the exhaust gas output, therefore tripping a code on the O2. I'll be following this one, for sure.

[DriVer]

Originally Posted by azstarr

Update: Well, finally got a TECH II to check out codes (local GM dealer did it for free). They confirmed what my reader told me, both O2 sensors showing bad; P0151 (bank 2 sensor 1 low voltage) and P0131 (bank 1 sensor 1 low voltage). Tech said that probably when the manifolds cracked the sensors became clogged with carbon.

I can confirm that the problem you described has affected my engine in a similar manner. I had both exhaust manifold gasket leak, R/S 1st and then the following year, the L/S. Since the replacement of the gaskets, I observed the MPGs tank. Later, I found out I had a bad O2 sensors so I had both sensors replaced.

It's been fine ever since MPGs are back. (Not stellar but back none the less )

[DriVer]

Originally Posted by rgreen45

Almost any other mechanical/electrical issue can cause a fault in the exhaust gas output, therefore tripping a code on the O2. I'll be following this one, for sure.

Would you please go to work!

[rgreen45]

Originally Posted by DriVer

Would you please go to work!

I gotta leave in 5 minutes. Clock in is 8:30 and it takes me 20 min to get there

[DriVer]

Originally Posted by rgreen45

I gotta leave in 5 minutes. Clock in is 8:30 and it takes me 20 min to get there

Have a good day!