Excellent info, appreciate that!!
FYI: SCV6 cylinder numbering
- Thread starter Michael Gain
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In the end I replaced the #6 Ignition Coil and all 6 spark plug, with no change. Also replaced the Air Charge Cooler Temp Sensor (since I am getting a P026A-00 code and its a $35 part) but alas, I believe my issues are actually related to the aux water pump itself... 
jlglr4
Full Access Member
i’m not sure why bad aux pump would cause misfire. I understand that it would give the p026a code and run less efficiently, but bad misfire on #6? Has any other work been done recently? Has it overheated or coolant levels dropped?
Not over heating and coolant level is fine.
I’m pretty sure I’m getting detonation, which after enough fouling of the plugs would lead to misfires. #6 hasn’t misfired since changing out that coil, but 1, 2, and 3 started misfiring a couple times. As long as I don’t get on the gas, I don’t get misfires. Climbing hills is where I really notice how underperforming the engine is doing.
As I understand it, the charge air is compressed air air exiting the supercharger going to the cylinders. The cooling action of that charged air occurs via the coolant being pumped by the aux pump. If that pump isn’t doing its job, the fuel/air mixture ratio will be less than optimal and the engine will not produce the proper power. And I’m definitely feeling that. This scenario could lead to fouled plugs ergo misfires.
I need to dig into the System Description and Operation again.
jlglr4
Full Access Member
That’s correct - sc compressing the air also heats it up, and the intercooler tries to bring that compressed air temp down as much as possible, increasing o2 density. If the air is warmer than expected, I assume the engine will compensate with less gas to keep the fuel mixture correct, but the net effect would be a little less power and possibly a higher running temp (not sure how much extra cooling capacity the system has via the thermostat to deal with hot intake air). I suppose that also could contribute to the pre-detonation.
Since I thought you were getting a misfire only in one cylinder, I didn’t think sc cooling would be the cause as it would affect all cylinders roughly the same. But since you are misfiring in other cylinders and both banks, then maybe that’s it.
My concern re coolant was the possibility of an air pocket in the intercooler giving a false temp reading.
Couple other possibilities just to put it out there: First, there might be a fuse and/or relay for the aux coolant pump, and corrosion in the connector might also be something to check. Second, I believe the p026A code is a discrepancy between expected compressed air temp and expected ambient intake temp, so the error could possibly be in the ambient intake temp sensor - though I’m not sure which sensor is used. I think the MAF sensors have a temp sensor component, so that’s maybe the reference temp used for the calculation.
Good luck with it. Let us know what you find.
Since I thought you were getting a misfire only in one cylinder, I didn’t think sc cooling would be the cause as it would affect all cylinders roughly the same. But since you are misfiring in other cylinders and both banks, then maybe that’s it.
My concern re coolant was the possibility of an air pocket in the intercooler giving a false temp reading.
Couple other possibilities just to put it out there: First, there might be a fuse and/or relay for the aux coolant pump, and corrosion in the connector might also be something to check. Second, I believe the p026A code is a discrepancy between expected compressed air temp and expected ambient intake temp, so the error could possibly be in the ambient intake temp sensor - though I’m not sure which sensor is used. I think the MAF sensors have a temp sensor component, so that’s maybe the reference temp used for the calculation.
Good luck with it. Let us know what you find.
Great info, I’ll check these items out as well.
Attached photo is what Topix attributes the P026A code to and what lead my down the aux pump path.
Attachments
FWIW, I ended up isolating the issue to a bad fuse, that hasn’t blown, but when I swapped the fuse with another, the EAS started barking. Swapped for a new fuse a voila, the truck actually pulls now and doesn’t feel so bogged down.
Unfortunately, damage to the left cat has already occurred (P0430)
I’ll need a new one at some point.Could you please let me know which fuse you replaced? ThanksFWIW, I ended up isolating the issue to a bad fuse, that hasn’t blown, but when I swapped the fuse with another, the EAS started barking. Swapped for a new fuse a voila, the truck actually pulls now and doesn’t feel so bogged down.
Unfortunately, damage to the left cat has already occurred (P0430)
Sorry I never responded to this. In the end, in August ‘22 the #3 cylinder failed somehow, scored the sidewalls, blew oil, engine was toast. Warranty spotted larger tires than OEM and canceled my warranty, putting me on the hook for nearly $20K.
Took forever to get an engine from the UK (via the dealer), so I got one from the excellent guys at Roger Parts Depo for a partial trade on my buddy’s bum 2016 LR4 that he gave me. FINALLY just picked up the LR4 today and she’s humming along. Somehow Bank 2 Sensor 2 (mid-left O2 sensor) failed and cause another check engine light during their road tests. I ordered one from FCP Euro and installed it this evening. So that works.
But again, the Charge Air Cooler DTC P026A popped up again. So I need to check the fuse. So weird lol. I’ll let you know which one it is, it’s been so long. It may be the relay…
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