Need Repair Info for 960 Codes 121, 322, 512

[meatball1]

Greetings all from Upstate NY! I am a Volvo novice looking for some direction and/or advice....

My check engine light is on in my '93 960 wagon and although it's old enough not to be a factor for the NYS vehicle inspection and doesn't seem to be affecting the way the car runs, I would like to see if I can fix the problem

If I am reading the code right, I get the following:

121- mass air flow or map sensor signal
322 - mass air flow sensor burn off signal missing
512 - O2 sensor control problem engine running lean

Can anyone tell me what these mean and what is needed to fix them?

[DanR]

Even though the engine is running smoothly, it will be running too rich and over time it will waste fuel and cause the convertor to over heat and die.

Code 121 - MAF sensor signal - I think 322, the burn off, are related. Have you cleared the codes and did they return?

Here are some things to check out that are simple and only require a volt/ohm meter.

With the ignition off, disconnect the MAF, on the connection plug, with the wire lock upward and look at the slots, slot 1 is on the right, slot 6 is on the left, connect an ohm meter to slot one and ground, reading should be approx. 0.

Still with ignition off, connect an ohm meter to slot 2 and ground, should read approx. 0.

Ignition on, MAF still disconnected, do not disconnect or connect the MAF with the ignition on. With ignition on, measure voltage from pin 3 and ground should read 0 - 0.5 volts.

Ignition off, measure with an ohm meter slot 3 and ground, should read approx. 11 ohms.

MAF still disconnected and ignition on, slot 5, volt meter and ground should read battery voltage.

Ignition off, connect an ohm meter to slot 4 and ground, should read very high or infinite resistance.

MAF disconnected, ignition on, connect a volt meter between slot 4 and battery postive, should read battery voltage.

If any of this does not measure up, then look for corrosion or broken wire to the ecm, especially at the large 54 pin plug on the wheel well under the black cover.

If the reading on slot two is different, look for a broken wire on the driverside engine mount bracket, there is a bundle of wires crossing over the bracket and a ground wire should be fastened to the bracket.

Code 522 could also be related to the 121 code. Check out the MAF first, and see if the takes care of the fuel trim code.

DanR '94 964 342,000 miles (108,000 on the new engine)