1.9gti cat engine management light when warm

[damo 17 2 Cars]

Hi, after some pointers, replaced my starter from the top so the throttle body and water pipes came off. Started fitted etc and now when it warms up when I give it some revs it throws my management light.

 

Turn the ignition off and restart and it comes straight on. If I disconnect the battery is goes off but again it warms and throws the light.

 

I'm thinking lamba sensor but I never went near it! Checked the brown plus and cleaned it up. So I can't see it being wiring.

 

So any ideas on what to look at ? 

[SRDT 146]

You can start by asking the ECU what's wrong:

 

[DamirGTI 323]

Possibly EVAP solenoid valve , if you've left it unplugged ..

 

Two of the most common "faults" triggering check engine on Motronic 1.3 from my experience are : lambda sensor and EVAP system .

 

Lambda sensor , usually you'll find wet/oxidized sensor connectors .. as they're situated low down by the chassis rail , moisture/rainwater from the road shifted by the spinning wheel/tire ends up "showering" the connectors . This will manifest as an "mixture code" , No.52 or 54 something like so cant remember ..

 

EVAP system , solenoid valve (people tend to remove the entire EVAP system , but then it lights check engine all the time , needs just the solenoid left connected or in the absence of the solenoid , resistor soldered across the solenoid connector to "mimic" solenoid presence .)

 

As above , bonus on a Motronic 1.3 system is you can "chat with it" , run diagnostics and see which numbers it displays .

 

 

D

 

 

[damo 17 2 Cars]

Thanks. EVAP system ? Any one got a picture? I think it's the thing near my power steering bottle. From passenger side in the engine bay. I hadn't touched it. Confused as it was fine till I switched the starter so must have disturbed something. 

 

thought it was strange it only did it when warm and when I rev the engine.

 

[SRDT 146]

The ECU is powering the valve as soon as you start the engine but I don't know if the ECU is checking that there is a valve all the time or just when it goes on "EVAP mode".

This "EVAP mode" is using the lambda sensor so it won't start until the engine is warm enough.

 

[damo 17 2 Cars]

So there's a pipe from the throttle body going to this ? I did take the throttle body off and there is something passenger side front on the engine bay that may be a evap? 

 

I took the air flow bits off to double check the wiring as I must have disturbed something. 

 

I thought on the throttle body underneath there two fat pipes on for cooled, one looks to go to the sad under the dizzy area on engine. One to the header tank and one thin one to the inlet manifold. Then there's a load of wiring and stuff between the battery and front. I have the pas bottle etc there. This is where I think this evap is right?

 

 

[DamirGTI 323]

Yes , it's connected to the inlet (it purges fuel vapors in the inlet manifold to be burned , mixing them with regular air/fuel mixture) , black valve golf ball size with one 2pin connector and two pipes/hoses on ... usually situated battery front , around/under throttle body area (No. 34 and 4 on the diagram) .

 

Check if all hoses are connected and hose clips tightened ..

[damo 17 2 Cars]

Thanks for that. Is there a part number in the document you got the pictures from ? 

[DamirGTI 323]

For the solenoid ? , if so it's : 1628 F0

 

Unlikely to be bad solenoid , if you suspect it being bad , quick and simple multimeter check will reveal if it's good or bad - if good , should read 1200 ohms across the solenoid terminals .

 

 

But better than guessing game , run ECU self diagnosis and see which codes it displays .. procedure might seem peculiar , but it's really simple connecting the diag. socket and counting the flashes .

Lots of videos on youtube also on "how to" self diagnosis procedure , on pre OBD cars .

 

D

 

[damo 17 2 Cars]

Got the ECU codes. It gave 12, 34, 11. So the codes 34. I'm I right that this is the solenoid, it's a canister purge solenoid valve. 

 

I'm I right it's the part as mentioned before, part number 1628 F0., Is there a full part number as a few flavours come up ending in those numbers.

Edited August 14, 2021 by damo

[Thijs_Rallye 86 4 Cars]

You can also insert a 1200 ohm resistor in the connector for the time being. But the EML will not cause a de-rate or anything.

[DamirGTI 323]

That code 34 is , the evap solenoid .

 

However , me thinks it's unlikely bad solenoid .. especially as this problem occurred after fiddling with the intake pipework .

Recheck all the hoses/pipes , clips , see if any of the hoses cracked/split .. and check the solenoid connector , peel off the rubber boot and see if any of the two wires under broken off from the connector terminal or the terminals hasn't made solid connection with the solenoid (ie , connector terminals pushed back) .

 

If you suspect the solenoid , as above , just bridge the solenoid connector with 1200 Ohm resistor that'll clear the code if it's really the solenoid going bad .

If you do not have the entire EVAP system functional , and thus not using it , solder on the resistor and forget about it . 

 

OE part No. for the solenoid is : 1628 F0 , Bosch No. is : 0 280 142 157 .

They're pretty common on all kinds of car brands/makes from the 80's/90's .. all have the same solenoid , base models too , only they had to be equipped/models with the EVAP system .

 

D

[damo 17 2 Cars]

Thanks guys, I'll look at the wiring and the pipe to the throttle body. But the resistor sounds like a good fix. 

[damo 17 2 Cars]

Checked ove the pipes and the wires look good. Did think of the volt meter test but no idea where in the loon they go to. I've ordered a 1.2 kohm resistor 2w to pop on the plug. 

 

As it's fine to drive with the engine management light with this fault and the resistor stops the light anyway.