Piston Slap: Sounding the Alarm on a Bad Sensor?

Diana writes:

Hi Sajeev!

My husband, rrhyne56, gave me your email address, because I have a question about my 2008 Honda CR-V.

The alarm goes off, in the middle of the night, only when the temperatures are freezing. Unlocking with the FOB, stops it. But, the FOB will not lock the car. I have to open the door, close it and then the FOB will lock and set the alarm again.

Hope you can help, because I’m losing sleep. Maybe my car wants us to move to a warmer place… 😉

Sajeev answers:

I don’t work on commission, yet I love getting referrals!

Assuming this is a factory Honda alarm, I’ll bet there’s a bad door/hood/hatch sensor freaking out the system. The Internet says a weak battery is a major concern, so ya better test that first. 

If the battery passes but there was recent collision repair, I reckon the affected area also needs a new sensor. More to the point, after I wrecked my Mark VIII, one of the first things I did was disconnect the hood sensor: it mercilessly honked as I tore off damaged panels. Since my diagnosis was pretty damn obvious, I bought an NOS Ford sensor and cleared one of the easier hurdles on that project.

If the CR-V has no recent collision repair, either disconnect or clean the sensors. I couldn’t google the Honda diagnostic, but the logic is to disconnect a sensor, tricking the computer into thinking everything is fine. The trick might also entail jumping the wiring with a metal paperclip. Watch this video, ask someone smarter than me and/or experiment yourself by starting without the paper clip.

I reckon you need a new hood sensor, as it had enough of having a hood slam down on it. I certainly don’t want that thing slamming down on me for 12 years.

What say you, Best and Brightest?

[Image: Honda]

Send your queries to sajeev@thetruthaboutcars.​com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.