Causes of P068E code
From what I’ve seen in the shop and based on official repair info, the most common reasons for a P068E code are:
- A worn-out or faulty glow plug in cylinder 8 (this is the big one, and it happens a lot more than people think)
- Broken, corroded, or shorted wiring in the glow plug circuit
- Loose, dirty, or damaged connectors at the glow plug or controller
- A malfunctioning glow plug timer or controller module
In my experience, it’s usually either the glow plug itself or a wiring issue, but I’ve also seen bad controllers cause this headache.
Symptoms of obd code P068E
When this code is active, you’ll probably notice a few things. The most obvious is that the engine might be hard to start, especially when it’s cold out. You might also see a check engine light on the dash. Other signs include rough running right after startup, excessive black smoke from the exhaust, sluggish acceleration, and sometimes even a drop in fuel economy. Occasionally, you’ll get misfire codes stored as well. If you notice any of these, it’s a good idea to get it checked out sooner rather than later.
Diagnosis steps for P068E
Let me walk you through how I handle a P068E code when it rolls into my bay. First thing’s first: I pop the hood and give everything a good visual once-over-look for fried wires, loose connections, or crusty corrosion right at cylinder 8’s glow plug and its harness. If you’ve got a buddy handy, have them crank the engine while you keep your eyes peeled for any sparking or wiggling wires. Once that’s done, I hook up the scan tool, pull every stored code and freeze-frame snapshot, and take notes on what was happening when the code set. I’ll clear the codes, fire the truck up, and see if the code comes back after a decent drive. If it does, time to dig deeper. I’ll yank out the number 8 glow plug and bench test it-hit it with battery voltage (watch your fingers, these things get blazing hot in a hurry) and see if it glows cherry red. No glow? It’s toast. If it gets hot like it should, I’ll grab the DVOM and check resistance against factory specs. Don’t overlook the fuses and relays-sometimes they only fail under load, so don’t just eyeball them. If everything so far checks out, I’ll use the scan tool to command the controller on, then measure voltage right at the plug. No voltage? Odds are your controller or timer is the culprit. And here’s a pro-tip: make absolutely sure you’re working on cylinder 8-mixing up cylinders is a classic pitfall even seasoned techs slip into now and then.
Common mistakes when fixing dtc P068E
One thing I see a lot is folks assuming the problem can’t be the glow plug itself just because the code says ‘control circuit.’ That’s not true-a bad glow plug can absolutely trigger this code. Another common mistake is testing the wrong cylinder-always confirm which one is number 8 for your engine. Skipping the basic visual inspection or not checking fuses under load can also send you down the wrong path. Take your time and check the simple stuff first-it saves a lot of headaches.
Seriousness of obd2 code P068E
I wouldn’t brush this one off. When the glow plug circuit’s not right, you’re setting yourself up for cold-morning misery-hard starts, rough idle, and a whole lot of unnecessary wear on your engine. I’ve seen trucks left unchecked with this code throw thick smoke, stumble out of the driveway, and even end up with fried controllers or PCM issues down the road. If you count on your diesel, don’t gamble with P068E. Get it sorted before it leaves you stranded when you need it most.
Repair solutions for P068E trouble code
Here’s what fixes P068E in my experience:
- Swap out the bad glow plug in cylinder 8-don’t cheap out, use quality or OEM parts
- Chase down and repair (or replace) any busted or corroded wires and connectors
- Clean and snug up every electrical connection in the circuit
- If the controller or timer isn’t sending voltage, replace it
- Don’t forget those fuses and relays-if they’re weak or blown, swap them for new ones
Stick to the manufacturer’s test steps and parts, and you’ll keep headaches to a minimum and reliability sky-high.
Conclusion
So, here’s the bottom line: when you see P068E, your PCM isn’t happy with the voltage at cylinder 8’s glow plug. That spells tough starts, rough running, and-if you let it ride-bigger headaches down the line, especially when the temperatures drop. Start with a sharp eye and basic electrical checks, then move on to glow plug and controller testing if needed. Nine times out of ten, it’s a bad glow plug or some crusty wiring. Don’t let it slide-get it fixed fast and your diesel will thank you every time you twist the key.
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