cat light come on when starting

5p4no

New Member
Hey guys im knew to the forum but im trying to figure out this problem with my lil zlr

when i start the car up the car starts fine but the cat light comes on and stays on and sets the car to idle at 500rpm and seems as if it wants to die as soon as u press the accelrator boom it comes straight up to idle at 900 and seems fine im stumped as to what it is??? im running a mines ecu with a front mount sard fuel pressure reg 3 inch exhaust with no cat im pretty sure has anyone experienced this problem i cant seem to figure it out??
 

PobodY

Moderators
Staff member
You've got no cat, but the cat light is coming on? - Is the probe actually connected to anything or are we talking about an electrical short here?

Start with the simple things; is the MAF element clean, do you have any vaccum/boost leaks (although that usually puts the idle speed up rather than down), is the TPS correctly adjusted? - Did you change anything? I assume it was running fine, and now it isn't?

The slightly scary suggestion is that if the cat sensor is connected and the light is coming on because the exhaust is red hot, and the idle is terrible, then maybe you're not putting enough fuel in and it's running really lean. - Maybe put the standard FPR back in and see if that fixes it?
 

geoff pine

Well-Known Member
When you say cat light it must just be the warning light looks like a small sausage The connection is under the drivers seat carpet un plug it and it should stop . You then need to sort out your fuelling problem is it a real sard regulator or one of the meany fake ones around ?why did you fit it in the first place .
 

PobodY

Moderators
Staff member
Mine is certainly unplugged, but some of the decat pipes retain a mounting for it. - It's not doing anything, and it shouldn't be connected to the ECU anywhere... but people have reported odd effects when there's a short between the cat sensor and something else.

You're obviously thinking the same thing I am Geoff; the Mines ECU isn't expecting anything other than standard injectors and fuel pressure. I know Ed isn't particularly complimentary about the map on them either.
 

5p4no

New Member
the wire for cat it not plugged in cauz some genius who owned the car before rounded the nut off so its just tucked away not plugged in and ive checked teverything the tps is fine cleaned out the afm and i bought the car with the fuel reg in it looks like a legit one for sure and i did try and put the old fpr in because i thought it was a lack of fuel pressure on start up but still did the same thing?? and ill unplug the sensor under the drivers seat tomoz see if it makes a differnece
 

vss irvine

Well-Known Member
Look under the drivers seat. Theres a multiplug that goes to the cat heat sensor. Unplug it.

All the cat light does is tell you when the cat is hot or overheating. If its lighting up on start up its probably shorting out on something due to vibration.
 

johnny gtir

Well-Known Member
As above and i would be checking fuel pressure just as said a lot of fakes out there that wont hold pressure. Might look ok standing still on idle but once driving is it regulating right. This said why was it there in first place before you just go putting standard one back on same goes for any part.
 

5p4no

New Member
it has always dones this since owning the car which is annoying and yes it does have a gauge and is running at idle 3bar and on full boost around 4bar and ive installed a det fpr cauz i could not find one specifically for a gtir but was a turbo fpr and still had the same problem i checked under neath the drivers seat and unplugged the sensor for the cat light and started the car it was still the same plugged it bak in still the same!!! i found also another 4 pin plug next to it but was not connected to anything does anyone know what this may be???
 

whytie

Active Member
The plug for the cat is under the carpet under the drivers seat if I rember correctly, maybe your un plugging the wrong one.
 

5p4no

New Member
hey guys unplugged the wire for the cat sensor then procceded to then start the car after but it still did the same the cat light came on until u revved it and then goes away im thinkining it must be a wiring issue does anyone have a wiring diragram for the two wires for the sensor????? like were it connects to??
 

5p4no

New Member
did a little bit more investigating regarding the cat light on startup i traced the wire all the way to the corner of the dash were it plugs into a big multiplug then continues into the loom for the cluster i found continuity off both the wires to the connector to the big multiplug so then i decided to take apart the dash surround to double check the wiring for the cluster had a good look at all the plugs seemed ok but tried continuity again from the wire to the multiplug at the bak of the cluster and found one wire which should go to light up the cat light was not gettin powered from there buy another which on the back of the cluster which reads battery so this was weird to me but i decided to start the car without the cluster and boom fired up fine straight away seemed very good so i turned it off and on and was mine no cat light i plugged that one multiplug in and immediatley cat light comes on soo weird lol
 

Nick K

Member
Has anybody messed with the cluster membrane? Just take the bulb out and forget about it!! Does sound like it's getting a feed from maybe the alternator light or oil pressure switch?! Does everything else work correctly on the cluster regarding warning lights etc !?
 
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PobodY

Moderators
Staff member
Did everything else work without the multiplug? - I'd leave it disconnected if it did.

The ECU shouldn't pay any attention to the catatlyst sensor; it really is just there to let you know when it's hot enough to start a fire... but you're not the first person to find some kind of short circuit that upsets the running of the car.
 

johnny gtir

Well-Known Member
Dont remove the bulb or leave it unplugged at cluster just under the seat and carry on somethings as you say not right find the problem with multi plug etc would be my advice
 

5p4no

New Member
still playing up even wen the cluster isnt plugged only happens after the first start like for example it will be first cold start will idle fine to dramas as soon as u turn it off an on again same thing its really starting to do my head i pulled the dash out so i can confirm there is not cuts in the wiring which there isnt but still cant find out y the sensor is coming on even when its on plugged im thinking it may be the ecu
 
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