I recently swapped out the coolant temp sensor on my 1989 244 with a new Bosch OEM replacement. It didn't have an error code at the time, but I had the intake manifold off so I replaced both temp sensors, heater hoses etc... When I put her back together I got a 2-2-4 error code for a faulty coolant temp sensor.

I'd really like to clear the code and see if it sets again, but I can't get rid of it. I left the battery disconnected overnight and it is still there. I have tried clearing the codes at the diagnostic unit by holding down the button twice for five seconds. I removed fuse 4 (not sure that is the right one), no matter what I do, I still have a 2-2-4 error code on socket 6.

Any ideas?

Ryan

Thats an Ez-k code. The unit may generate the code right away if the resistance is way out of spec.
Have you checked the resistance compared to ground on the temp sensor wire at the connector for the ignition ECU to see if it is within spec? I would compare it with the temp sensor wire to the 2.4 control unit. The resistance should be the same.

Did you check the ground wire connections on the intake manifold? You can get some weird errors if these grounds are not solid

Are you sure you have the right sensor? The older type will fit and plug in but it will not work with LH 2.4. The 2.4 sensor is a dual thermistor and needs to be grounded to the block to work. I am pretty sure the older type are single thermistor with one of the lead wires acting as the ground. The 2.4 sensors are usually black.

You could also try putting the old sensor back in. Its a real PITA with the manifold on but it can be done. I usually take one of the idle air hoses off to make access a bit easier, but even then I end up cursing and get a scratch or 2 on my arms. You could do a quick test by just plugging the old sensor in and grounding it to the engine. If the code goes out there must be something wrong with the new sensor.

I'm away from home and don't have my book but I think you might be putting the pin in the wrong socket or timing has to be longer than 5 sec but not too long after certain flashes.

I think I remember that there are two parts to the system.

One is for reading codes.

One for testing component operation.

When reseting/clearing you have to do something a little different for clearing a section.

I suggest going back slowly through the steps of the Bently book. For me it was confusing or I didn't remember it clearly. I read and did the procedure a few times before it worked.

Undoing the battery does not work on all the codes and give you he 1,1,1 on these years, as I can remember from here from home.

Phil

um isn't it possible that the code won't clear because the problem exists in the first place ?

The code should report back cleared before the car is operated again.

I don't know how long it takes for the code to be recorded.

There are two sections memory and component testing i.e., throttle switch.
Socket # 2 and then socket #6 # 2 I think is the only one that clears.

I'm leary of passing out miss information. I like to use my manuals. I have found that the pages don't fade in and out like my memory!


Could be the harness wiring back to the computer. I would pull the plug on the ECU and try to read back to the coolant sensor for high ohms cold and low ohms at operating temps. 2300 to 200-300 ohms as I try to remember.

I'm off house and dog sitting. Wives are off traveling. I'm going around repairing a Brother-in-laws variety of era vehicles. He just pulled out a 1950-03's David Bradley Garden Tractor that hasn' run in about 25 years. So, I mean all kinds of other interesting projects he has.

Been here 2 weeks and not bored yet! I'm just relaxing here.

Phil

Hi Phil,

Interesting vacation you have. How do you get wives to travel?

I've got (actually, Mrs. B has) an 89 245. All the codes are easily reset, along with any computer adaptation, by briefly removing and replacing the blade fuse under the hood. These EZ-K and LH2.4 computers have no short-term memory without the battery. They perform pretty much like I do, when returning from a vacation, starting from scratch.

I think Jessie has the answer here - the blue sensor probably got installed where a black one goes. Its thermistor is not referenced to ground, where the black one has two - one for ignition and one for fuel - with a common ground. If not, then there's an out-of-box failure from Bosch, just an unheard-of event in these days of global manufacturing competition. In either case, measuring the resistance from the ECU and ICU plug would lead to an "aha" moment.

The Brickboard is nice for when you leave the Bentley at home. The 7/9 FAQ serves well for engine diagnostics, where most systems are identical to 240s. Two weeks without a Volvo manual is OK, but try staying away from the computer and the BB for that long. Now that would be a vacation.

--
Art Benstein near Baltimore

There are two theories to arguing with women. Neither one works.