Hi, all,

I pulled the codes from A2 socket for "check engine light" and got codes 4-3-5 and 1-2-1. I understand the code 4-3-5, but need more detailed explanation for code 1-2-1. what does that stand for? Is it a serious problem? Thanks.

1995 Volvo 850

It's a code for your MAF sensor and at the moment I wouldn't worry about it as it's probably more an intermittant connection problem than anything else.
435 is slow O2 sensor so I'd replace the front O2 sensor, clear the codes and see if 121 returns. If anything, apply some dielectric grease to the plug terminals on the MAF meter and wire tie the plug wiring back onto the MAF meter so that the plug wire harness movement is minimalized (was once a campaign for certain years, after '95 I believe).

Thanks for your response. I cleared the fault codes (both 435 and 121) without changing O2 sensor. If the check engine light comes back on, I will have the sensor replaced.

Since I have no idea what the MAF sensor is for and of course don't know where it locates, I appreciate if you could describe in detail where it is. Thanks in advance.