Codes 2-3-2 & 1-2-3
 

My '91 240 just threw these two codes at the same time in this order:

2-3-2 . . . Lambda Adjustment . . . Check Intake Manifold
1-2-3 . . . Coolant Temp. Sensor Signal . . . Check Sensor

Relevant recent history: I changed the Tstat and Coolant about a month ago.

Despite the codes, she seems to be running fine for the moment. Any thoughts on what could cause these two codes to appear together? What should I be looking at?

Thanks for you in advance for sharing your experience and expertise

Grant

1-2-3 - signal missing form coolant temp sensor (the engine 2 pin sensor not the gauge 1 pin sensor)

this is probably causing you to run rich, throwing code 2-3-2 which is you are running too rich or too lean

check your temp sensor wiring and or replace the sensor.

its easy to test at the ECU on pins 13 and 5(ground)

readings should be about 2000-2500 ohms when cold and about 200-350 when hot

Thanks for the info, Nichals. That makes sense; I believe she is running a bit rich.

I have a couple more questions, if you'll indulge me:

I haven't used a multi meter to check resistance at the ECU (or any other electrical levels for that matter.) When you refer to values when hot/cold, I'm assuming that means with system live/off. Is that right? Is it better to test one way or the other?

Second, any advice for reaching the temp sensor? It's buried pretty far back and down.

Thanks again,

Grant

temperature sensors vary their resistance with high resistance when cold, low resistance when warm. There's charts to get to the exact value but for the sake of fault testing, you should see something like 3000 ohms at room temp and under 100 ohms in a warm engine (ie 150-200 degrees). On my S40 and 850, removing the temp sensor requires removing the thermostat cover so if you decide to do that, time to do a new thermostat, temp sensor and the overflow's pressure cap. Just did this job today on the 850 in fact...

re: hot vs cold test. Get the engine hot, shut it off, unplug the ECU, and measure the resistance at the appropriate pins of the ECU plug... then wait a couple hours for the engine to cool down, and measure it again. general idea is a fairly low resistance for a hot motor and a fairly high resistance for a cold motor. the exact value isn't as important as seeing that it changes and is the right order of magnitude.

on a redblock, (240, 740, 940), the temp sensor is on the head, under the intake manifold, don't need to touch the thermostat to get to it.

pierce, thanks for clarifying the testing procedure for this. Have you replaced the coolant temp sensor? Can it be reached without removing the intake manifold? Any tips about removal/replacement are greatly appreciated.