Intermittent CEL on Civic VX

[evan.heidtmann]

Hey everybody, I recently bought a VX with 137,000 miles and it's mostly in great shape. But very occasionally the check engine light comes on. I'm posting here to see if anyone has seen this before, or has any ideas about it. Here's the story.

I live near the top of a big and rather steep hill. When I drive out from home, I can either go up or down the hill. If I go uphill, I don't see the CEL. But if I go downhill with a cold engine and engage engine braking (so the fuel injectors are cut off), I will usually see the CEL turn on after 1-2 minutes of descending.

Once on, the light stays on for the rest of the trip, but will disappear if I shut off the engine and start it again.

The self-diagnostic procedure shows no code after restarting the engine. Once, jumpering the appropriate leads when the engine was running and the light was on gave code 48 -- the LAF sensor.

I was taking the car to a shop for some other work, and had them look at this problem too. They did the self-diagnostic, read code 48, and then checked some loose connections between the LAF and the ECU. Since then I've seen the light come on 1 out of 2 times descending the hill.

My next step is going to be to check the connectors myself. The service manual gives two connector numbers to check.

I'm interested to hear your thoughts on this. Thanks for your help!

[GasSavers_TomO]

LAF troubleshooting Code 48 Try that first and let us know what you get.

Sounds possible that your LAF is on it's way out or you may have a faulty heater. The heater should be able to maintain the necessary heat to the LAF during your DFCO (Deceleration Fuel Cut-Off) and not trigger the CEL.

[evan.heidtmann]

Thanks, Tom. The heater explanation sounds likely.

I will follow the flowchart and let you know where I end up. I expect I'll get to "Intermittent failure. ... C211 ... C111 ...", which are the connections I plan to check.