2013 Honda Accord - P0108 Code (MAP Sensor Circuit High Input)

SOLVED! Hello @qatmech and @wqshaider! I finally got the new MAP sensor (I went with a Denso one) and installed it this afternoon. I disconnected the battery like you said, @wqshaider. I started it up, and the idle was immediately smoother. I took it for a drive on the Expressway, and the power is completely back! No more sluggishness. The check engine light is off and the code has not returned. Thank you both so much for your clear, step-by-step help. You saved me a lot of time and money, and I learned a lot about how the MAP system works. This forum is a fantastic resource!

Update: I got a multimeter. I checked the voltage at the connector with the ignition ON. I was getting almost 4.8 volts on the reference wire, which seems close enough to 5V, right? So the ECU is sending power. I also checked the continuity for the ground wire, and that was good too. I couldn't see any damaged wires in the visible harness. I think you guys are right, it's pointing to a faulty sensor. I couldn't find a friend with a car to swap with, so I'll just order a new one.

@johncarguy, following on from what @qatmech said, if the wiring looks intact, the sensor itself is the most probable cause. They do fail over time. Before you buy a new one, see if you can find a known good one to test with. Do you have any friends with a similar Honda? Swapping the MAP sensor for a few minutes is the fastest way to know for sure. If the code clears and the idle smooths out with the other sensor, you've found your problem. The part number for your 2013 should be common. You can find a good used one at the scrapyards in Industrial Area or just get a new one from the parts shops.

Thanks, @qatmech and @wqshaider! Really appreciate the guidance. I checked the vacuum hose just now. It looks fine visually – no obvious cracks, and it's on tight at both ends. I gave it a gentle wiggle with the engine running, but the idle didn't change, so I don't think there's a leak there. I also unplugged and re-plugged the electrical connector. The pins looked clean and straight, no corrosion. I haven't done the multimeter test yet as I need to borrow one from a friend.

@johncarguy, @qatmech is spot on about the vacuum hose. That's the most common culprit. To add to that, if the hose looks good, the next step is to check the sensor itself. You can do a quick test with a multimeter. With the connector unplugged and the ignition ON (engine OFF), check for 5 volts at the reference wire on the sensor side of the connector. If you have that, then the ECU is providing power correctly. If you don't have a multimeter, a "poor man's" test is to carefully unplug the MAP sensor with the engine idling. If the idle doesn't change or gets worse, the sensor is likely dead and not communicating with the ECU.

Hey @johncarguy, common issue on these cars. A P0108 means the ECU is seeing a higher voltage from the MAP (Manifold Absolute Pressure) sensor than it expects, usually when the manifold pressure is low (like at idle). First and easiest thing to check: inspect the vacuum hose that connects to the MAP sensor. It's a small, black rubber hose. Make sure it's not cracked, loose, or collapsed. A vacuum leak in that hose or near the intake manifold can cause this code. Also, take a look at the electrical connector on the sensor itself. Make sure it's clicked in properly and the pins aren't bent or corroded. The heat here in Qatar can be brutal on plastic and rubber parts.