240 lamda light

The lamda light (which is for the O2 sensor right?) is on, on my 92 240.
Here's what I've done recently:

1. Did an oil change and replaced air filter
2. Did an e-fan conversion
3. Drove the car very hard to test out the e-fan effectiveness.
4. Next time I drove the car, the lamda light came on after a couple of minutes.

Is it likely that the o2 sensor is indeed stuffed, or could it be indicating something else? Is it just a coincidence that it's happened at this time?
What steps should I take now?GLIWD6Uh.jpg


  • I may be wrong, but I believe that lambda sond light is actually the 'check engine light'.

    92 is LH 2.4.

    Have you done the dance with the diagnostic connector and checked for codes?
  • 240240 @240 Canberra
    Ah, that could well be a possibility. I'll have a play with the diagnostics thing tomorrow.
  • Vee_QueVee_Que @Vee_Que South Eastern suburbs Melbourne.
    How often do you drive it hard?
  • 240240 @240 Canberra
    Not all that much really, I don't drive it like a granny but I don't frequently drive it really hard either.
  • 240240 @240 Canberra
    Right, I pulled ECU code 1-2-3, which apparently is "Coolant temperature sensor missing or faulty".
    Any idea why this could be?
  • jamesincJames @jamesinc Oz Volvo Ice Fortress
    edited March 2017
    Maybe the coolent temperature sensor is missing or faulty.

    Edit: check plug to sensor (it's under the intake manifold about half way back). If it is still attached, order a new coolant temp sensor (ECT).
  • 240240 @240 Canberra
    It's just odd that it should happen at the same time as I did the efan conversion etc, so if I did something to stuff it up it'd be good to know what it was.

    Google says there are 2 sensors, one for the ECU and one for the temp gauge. In this case it'd be the ecu one that's faulty, right?
  • jamesincJames @jamesinc Oz Volvo Ice Fortress

    If you switched to an e-fan, the different temp range the engine is operating at may be enough to trigger some kind of issue with an old sensor.
  • 240240 @240 Canberra
    Ok, so 2 questions:

    1) what does the ECU need the temp sensor for? ie, what, if any, damage will I do by continuing to drive the car?

    2) can my existing temp sensor be tested with a multimeter or something?
  • jamesincJames @jamesinc Oz Volvo Ice Fortress
    The ECU adjusts the fuel mixture based on the ECT output. If the signal is faulty, the ECU will assume your engine is very cold, and rich the mixture accordingly. It won't in the short term do any damage, but it will kneecap your fuel economy and power.

    My advice would be to just get a known working sensor and plug it in and see if the code goes away. They're not hard to come by, I should have one in the garage if you want to borrow it. I can mail it down with some stuff I need to mail to @paul0075
  • 240240 @240 Canberra
    OK that makes sense. The car seems to be driving normally but it could well be using more fuel I guess.
    Is the sensor different for LH 2.2 and 2.4? I know someone locally with a 2.2 one. Otherwise I might take you up on that offer.

    Oh, one other thing - should I clear the code and see if the light comes back on? Or is that just a way of temporarily hiding a problem?
  • If it's truly faulty the code will return again after clearing it.
  • jamesincJames @jamesinc Oz Volvo Ice Fortress
    Yeah the sensor is different
  • So back in march, @jamesinc sent me a known working ECU coolant sensor. I swapped it in, cleared the code and it was fine.
    However a couple of days ago the light came on again, the code once again is 1-2-3, meaning faulty ECU coolant temp sensor.
    Of all the things that could go wrong, what are the chances that two sensors would go bad in under a year? Coincidence, or do you think there could be something killing the sensors?
    (Only thing I can think of, is because I'm running an e-fan, the coolant might be running hotter...?)
  • Wiring harness disintegration maybe? Similar era in other models had trouble with wiring breakdown in lots of harnesses running near the engine.
  • Maybe, but I thought that was resolved by the late 80s? Mine is a 92.
  • Do / did you have a temp gauge faker, and if so, have you removed it? See cleanflametrap reference below.

    If not, have you experienced any brief periods of overheating?

    Does it come back quickly after you've cleared the code?
  • No I haven't removed the faker, although yes the needle occasionally gets about 3/4 up the gauge (I'm not using quite the right temp sensor for the e-fan so sometimes sitting in traffic it gets hotter than it should).

    I wasn't able to get it to go away at all even when I tried to clear the code.
  • ^If you don't have any coolant leaks, it's possible that the CTS has gone cactus. Although the temp faker may not be allowing you to see the full picture and the car may be running far hotter than you know, and that will keep setting a code. Had this happen when The Heisenburg (89 240 LH 2.4) developed a slow leak in a heater core hose after the engine mounts failed.
  • There is a very slow leak from the thermostat housing - I don't think I put the seal in properly.
    How does it affect things though?

    Excuse my ignorance, what's the CTS?
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