So I was driving down a residential street at 20-25 MPH and BAM! No power, severe misfiring like it's out of time. I limped it home and took the code off #6, 2-2-4 Coolant temp sensor signal.

One second it's running perfectly, the next I'm limping it home. No blown fuses. It starts fine, seems to idle perfectly, but push the gas while in park and it hesitates/misfires severely. Ease on the gas and find the sweet spot and the engine ramps up nicely.

Now, I know there are two coolant temp sensors and I think I've located both. One near the front has two wires, the other just behind it has a single wire. Am I right? Which one affects the ECU? How would I test the sensor?

And finally, I have my doubts regarding the legitimacy of this 2-2-4 code. Does this sound more like a crank position sensor failure? I'm new to this car and Volvo, so I'm a little timid about jumping in right now.

Anyone care to share some insight? Thanks.

 

Hmm. For it to just fail to work in an instant sounds like an electrical problem than sensor failure. Make sure the connections are secure. Clean the contacts. Make sure they are not bent.

To check the sensor, refer to this Engine Sensors page that deals with 7XX/9XX but applies to your 240 as well.

 

This sounds strange to just all of the sudden happen. The coolant temp sensor is the furthest one back. it is difficult to get out and some have removed the intake manifold to get at it. I would check the connection and wire first and reset the code. It's function is to tell the ECU that the engine is cold and it needs more fuel to start. Some cars had a separate cold start injector that was activated when the eng temp was below a certain value. Later cars just cycled the injectors more and for a longer duration to enrich the engine. Is the eng running rich and can you smell a lot of fuel. Pull a sparkplug and see if it is wet. You may have fouled the plugs and need to pull and dry/replace them. Try cleaning/check and reset and then start it up.

 

Thanks for the valuable input.

I gave the ECT connector a good shove from the backside to ensure it's seated. It was helpful to pull the automatic transmission dipstick for clearance around the back and under the intake manifold.

I also pulled the cover off the large ECU plug and probed pin 13 from prestart to operating temp and watched the voltage drop to ~.5 volts. The sensor seems to be within the spec listed on that page.

Still running like crap, but at least there are no OBD codes anymore.

The culprit? An 'Accel' coil from Advance Auto Parts that I'd installed as part of a shotgun tuneup. I put the original Bosch back on and it runs like a charm.

 

Problem Solved.

 

Well, yeah. I guess. No OBD codes and replacing the crappy aftermarket coil with the original one has resolved the misfiring. I guess I shouldn't have bought that brand of coil in the first place. Some reviews on the Advanced Auto website describe an extremely early and sudden failure; it must be common.

I'm not sure why a bad coil would have triggered an ECT code, so there may still be some problem there. All I did was ensure the connector is seated and verified the signal reaches the ECU and now there's no code for it anymore. 1-1-1 and 1-1-1.