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Oh no! Not again!

posted 12 Oct 2012, 17:45 by Robert Crane   [ updated 13 Oct 2012, 02:08 ]
Over the past few trips the "1-4 Slow Down" warning light has flashed occasionally on the dash. This is the same warning light for the cylinder bank that the ECU unit was changed a while back. About 20 minutes into the drive today the "1-4 Slow Down" warning light began to flash again. It kept doing so intermittently for the next few kilometers until the car went into "limp mode". Oh great, not again.

Remembering that by turning the car off and on "limp mode" can be reset. Question is, will the car restart if it is turned off? It should, and at worst simply remain in "limp mode", but you never know do you. After deciding to be brave and pull over, attempted to turn car off and on again. It started (phew) and "limp mode" was gone (hooray), however after a short distance again the "1-4 Slow Down" warning light had returned. Time to head back. On the return trip the "1-4 Slow Down" warning light continued to flash more than it had ever done in the past but luckily the car did not go into "limp mode" but you can certainly feel the electronic control unit attempting to shut down one of the cylinder banks. Luckily, it didn't do that permanently, just had to put up with some stuttering.

The initial reaction to these sorts of problems (especially continued problems like this) is always emotional and extreme. The trick is simply to get over it (things could be FAR worse) and work out what needs to be done to get it fixed.

After a quick email to Sal DiMauro from Racing Red it would seem that the most likely culprit is the thermocouple that runs from the catalytic converter to the ECU unit (F highlighted in the image below. The problem one is the one on the right).


So the recommendation is that this will need to be changed. A check around the Internet seems to indicate that these thermocouples are around $200 so that shouldn't be too bad.


A quick look under the car shows where the thermocouple connects to the catalytic converter, so it isn't too hard to reach at all and all seems to be in order. All the connections are solid so it isn't as though anything is loose. The connection at the other end of the thermocouple to the ECU is currently underneath a shield but undoing all that probably won't make much difference as the connection to the ECU is solid. So, looks like it is time for a new thermocouple.

Interestingly, comparisons to the good thermocouple on the left hand side seems to indicate that the problem one, on the right, is more 'worn'. It certainly doesn't appear to be the of the same vintage. There is also a small clamp half way up the body that holds the thermocouple in place and prevent it flapping around. At least there is on the left but not on the right hand side. There is no clamp or nut holding preventing the problem right hand thermocouple from flapping around. These two fact seem to indicate that the problem thermocouple has been changed or 'fiddled' with at some stage. Interesting.

So now the hunt is on for a new thermocouple. Sigh.
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