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Discussion Starter · #1 ·
About 2 months ago my Envoy out of the blue flashed “low oil pressure” on the dash and the engine cut off while driving. I was able to get it pulled off to the side of the road. Although it was idling roughly it did crank back up. I put my OBD II on it and got several misfire codes. In fear of harming the engine I had it towed to my Tennessee home. I replaced all 6 ignition coils as well as the 6 spark plugs. The car turned over and fired up but still read a misfire on cylinder 4. I pulled it back apart and found oil. A few days later I was going to have it towed to my Atlanta home as that’s whew my tools are and it was completely dead. I jumped it off, drove it on to my tow dolly and let it run, so to charge what I thought was just a drained battery. Got it home and of course it was dead again and had to be jumped off to get off the dolly. It has since then been on a trickle charge but will not turn over and reads “Unidentified Driver” when turning the key on. I am stumped at to what’s going on. Any ideas what I need to do to it in order for it to begin turning over again? I’ve taken the battery loose and hooked it back up and it reads the same “Unidentified Driver” on the dash and misfire on cylinder 4 on my OBD II… this is my baby and I want her back on the road. If anyone has any suggestions or knows the underlying problem as to what could be causing this please let me know. I work on all my vehicles personally and over the years have never ran into a problem like this. I’m self taught so I’m no pro but I’m definitely able, willing and accepting to learn what I don’t know.
 

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I have never seen "unidentified driver". I have however seen "Unknown Driver". This is normally a communications issue between the BCM and the Instrument Cluster. In the cases I have seen it is NOT going to cause a no crank or no start condition.

How old is this battery?
 

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Discussion Starter · #3 ·
I have never seen "unidentified driver". I have however seen "Unknown Driver". This is normally a communications issue between the BCM and the Instrument Cluster. In the cases I have seen it is NOT going to cause a no crank or no start condition.

How old is this battery?
I’m
I have never seen "unidentified driver". I have however seen "Unknown Driver". This is normally a communications issue between the BCM and the Instrument Cluster. In the cases I have seen it is NOT going to cause a no crank or no start condition.

How old is this battery?
I replaced the battery a year ago September. As for the “Unidentified and Unknown” it may very well say unknown.
 

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2004 chevy trailblazer_lt
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Welcome to the Forum!

Now to continue with where TJBaker was going on the diagnostic tree, I would go ahead and remove the battery and alternator from your Envoy and take them to one of the auto parts stores (O'Reilly, Advance, NAPA, Carquest, Autozone) that tests batteries and alternators for free, and have the battery load tested and the alternator tested to see if it is putting out the recommended voltage and that the DC voltage is clean and does not have excess AC ripple voltage on it, and that the internal diodes and regulator are functioning properly.

Then while those two items are still out of the Envoy, look over your battery cables to make sure they have not begun to deteriorate (as demonstrated by the presence of green grunge where the copper wires go into the battery terminals and lugs. Also make sure that where the negative battery cable connects to the engine block and the vehicle body are also nice and clean and tight. Same goes for the positive battery cable where it connects to the plastic box it initially goes into and then where it connects to the starter solenoid.

Dirty, poor, or bad grounds can cause all kinds of havoc with these vehicles. That's why every 2 to 3 years I check all the grounds on my vehicles for integrity. A hour or two here and there cleaning a bad ground connection or two can save you many hours of diagnostics and frustration.

Good Luck!
 

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Discussion Starter · #5 ·
Welcome to the Forum!

Now to continue with where TJBaker was going on the diagnostic tree, I would go ahead and remove the battery and alternator from your Envoy and take them to one of the auto parts stores (O'Reilly, Advance, NAPA, Carquest, Autozone) that tests batteries and alternators for free, and have the battery load tested and the alternator tested to see if it is putting out the recommended voltage and that the DC voltage is clean and does not have excess AC ripple voltage on it, and that the internal diodes and regulator are functioning properly.

Then while those two items are still out of the Envoy, look over your battery cables to make sure they have not begun to deteriorate (as demonstrated by the presence of green grunge where the copper wires go into the battery terminals and lugs. Also make sure that where the negative battery cable connects to the engine block and the vehicle body are also nice and clean and tight. Same goes for the positive battery cable where it connects to the plastic box it initially goes into and then where it connects to the starter solenoid.

Dirty, poor, or bad grounds can cause all kinds of havoc with these vehicles. That's why every 2 to 3 years I check all the grounds on my vehicles for integrity. A hour or two here and there cleaning a bad ground connection or two can save you many hours of diagnostics and frustration.

Good Luck!
@chem_man, thanks for the welcoming! I appreciate your response to my issue and will most definitely be doing as you advise ASAP. Any idea on what could be causing the oil leak into cylinder 4 that’s causing my misfire?
 

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You are quite welcome. Regarding the oil leak, it could be the valve cover gasket, leaky valve stem seals, etc. Start simple and check to see if the valve cover fasteners are tight. I think the torque spec is 88 inch-lbs. They sometimes loosen. Also check the ignition coil seal on the #4 cylinder while you are at it.

Another thing to do is to perform maintenance on the PCV system. There is no PCV valve, but there are a couple of hoses and a metering orifice. I'll refer you to this link for an explanation of the PCV system and how to clean it:


The video and information is from our resident retired but way too busy professional mechanic, Ravalli Surfer, who has an amazing knowledge of the various systems and proper diagnostic procedures. We are blessed to have him on here.

TJBaker is also a very talented and capable mechanic who knows how to get the most information out of the OBDII system and how the various modules communicate with one another. Another individual we are blessed to have on board. I feel like a lowly apprentice compared to TJBaker and Ravalli Surfer.

Good Luck!
 

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Discussion Starter · #7 ·
You are quite welcome. Regarding the oil leak, it could be the valve cover gasket, leaky valve stem seals, etc. Start simple and check to see if the valve cover fasteners are tight. I think the torque spec is 88 inch-lbs. They sometimes loosen. Also check the ignition coil seal on the #4 cylinder while you are at it.

Another thing to do is to perform maintenance on the PCV system. There is no PCV valve, but there are a couple of hoses and a metering orifice. I'll refer you to this link for an explanation of the PCV system and how to clean it:


The video and information is from our resident retired but way too busy professional mechanic, Ravalli Surfer, who has an amazing knowledge of the various systems and proper diagnostic procedures. We are blessed to have him on here.

TJBaker is also a very talented and capable mechanic who knows how to get the most information out of the OBDII system and how the various modules communicate with one another. Another individual we are blessed to have on board. I feel like a lowly apprentice compared to TJBaker and Ravalli Surfer.

Good Luck!
I will be back at my home where the Envoy is in the morning and plan to begin the process of elimination. Thanks so much for your help. I will let you know how it goes or is going once I’ve begun.
 
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