240 LH2.4 AT persistant code 1-2-3

Hi pals again!

Since the car was fixed three months ago, it remains parked most of time, so it can be a thing to consider.

Today, I get the volvo to take my dog at the doctor and after 10-20 minutes of driving, the CEL light comes on (AGAIN )
When came to home, the obd said error code 1-2-3 , but nothing is wrong with the 240: good start, no hesitates, no black smoke, no power loss.
So , what the hell it can be? I have cleared the error, but after 20 minutes of driving, comes on again.....
Your help will be appreciated, as usual
Gracias amigos y saludos desde chile

The LH2.4 greenbook describes the procedures for diagnosing trouble codes. 123 pertains to the coolant temp sensor for the fuel injection. Check the sensor and the connector for corrosion.

http://www.volvowiringdiagrams.com/volvo/LH%202.4/LH2.4%20Manual%20Complete.pdf

hiperfauto said:

The LH2.4 greenbook describes the procedures for diagnosing trouble codes. 123 pertains to the coolant temp sensor for the fuel injection. Check the sensor and the connector for corrosion.

http://www.volvowiringdiagrams.com/volvo/LH%202.4/LH2.4%20Manual%20Complete.pdf

Click to expand...

I have the greenbook and the car was with a set of issues before this one: black smoke, poor idle, soot, no start, etc. the car had a bad fpr (changed), a wrong ect (replaced by the OEM), bad O2 sensor (changed) , and bad pre pump (fixed). Everything seemed and work fine since these replacements, but it last only three months.... That is why I'm here again. If all that stuff was replaced by new ones, what it can be happening to get again the CEL on and 123 Code with no evidently signs of malfunctioning?

It could be a temporary break in the connection that was quickly restored. Check the terminals in the CTS connector to make sure the wires aren't backing out of the insulator. I've also seen the wire break at the crimp causing intermittent contact.

Thanks hiperfauto for your input. I'll try that. Any (or more) ideas to fight this annoying issue?

A bad sensor even though it is new. Assuming that because a part is new it can't be defective is a huge mistake.

Could it be thermostat?

Just curious, what brand was the CTS?.

Control temperature sensor . Am I right?

CTS = coolant temperature sensor. It should look like this.

Remember guys, codes on these old Volvos are commonly wrong. It isn't very good technology compared to modern cars.

ALWAYS consider that the fault is something different, or not quite, what the code is telling you. For example, I had an ECT code go off after an overheat. That was an example of the code being correct-"ish".

If I had to guess I would say bad wiring or connection could be causing this code. You need to get a needle, backprobe each wire at BOTH THE LH AND THE EZK BOX at the appropriate terminal and check voltage and/or resistance readings of the ECT sensor. I would also do a wiggle test at the computers by pulling on the plug and the wiring and see if I could get the readings to change on the multimeter.

You could also be running too hot or too cold, but probably not.

Or the aftermarket sensor isn't working properly with the ECUs.

Again, resistance values are where to start. Then also check resistance of the wire going from the sensor TO each computer. Make sure there isn't high resistance (more than an ohm or so) and see if you can make the values change with a wiggle test.

I had change the thermostat but no differences. And again... I drove the Volvo 20 mins and the CEL come on again. Now I going to test the wiring and will let you know. Greetings

Hola amigo al sur.

Something likely IS wrong. Without having car its tough, but something to consider is bad crimp schwarts. The crimps go bad from oxidation.

The computer is detecting a fault and its probably correct. You need to get out the multimeter and do lots of poking. I am going to a training session in a week to learn more about electrical stuff. Experience and training will lead you to the answer.

With me, same code, the sensor actually WAS bad. No connection between both terminals and copper housing. The 2 leads both need a resistance to ground corresponding with a temperature scale. One for the EZK ignition, one for the LH fuel injection.
Also check if, with both ecu's disconnected and the sensor disconnected, if there is any connection between the two wires, or with ground, indicating a fracture of the isolation.

The ground connection of the fuel rail is the ground connection for the ECT signal, so if you probe the ECU connector and find an out of range number, but the ECT itself measures in range, the ground connection there may be your problem.
Testing with a digital multimeter is going to give you better ideas than us making guesses online.
If it is fun to replace things for you, I'm sure we can tell you things to replace.
If it is important to find the problem, you will probably have to do the diagnostic work that doesn't involve replacing things.

I performed an ezk test and It throws the 224 code: ect sensor or wiring faulty. Which test can I do to undoubtely point the culprit?

I would do resistance tests.