Field Test Mode - CA20e ECM what does it do

[ffourc]

Can anyone tellme, what FIELD TEST mode actually does?

I know

it shows O2 sensor open/closed loop - and rich and lean

it turns on the radiator fans

it holds timing to 5*Btdc (assuming dizzy is set right) up to 3K revs. (when air load is low)

BUT what else does it do??

and most importantly what issues would cause my car to run 100x worse when I try to use field test mode.

thanx

[Jono]

Have you checked the FSM?

Why are you trying to drive it in test mode?

[ffourc]

The info I posted is from the FSM - I've also trawled the iternet to no avail

from the net: In some ECM's - field mode energises all the relays? servos? canno remember which or both!

why am I (trying to) driving in field mode - over the last 2 weeks my car has stalled 5x. and is showing signs of surge and stumble. erratic idle/hunting, occasional hard starting when hot etc. so the object of field mode was to test fuel properties ie rich /lean etc.

Now I'm pretty sure , the problem is electrical in nature (NOT dizzy/afm/tps) and I suspect a intermittent short is occuring somewhere and it is getting WORSE(which you'd suspect) . The fact that the car is much worse in FIELD MODE, might help me islolate the fault IF ONLY I knew exactly what field mode does different to Normal mode. comprende.

I've checked a bunch of wiring with the mutimeter(mainly continuity,some voltage), but the problem with intermittent problems is that the wiring may test ok most of the time - except when it isn't - eventually(getting sooner everyday) it'll probably fail completely and I'll find it - but I don't want that to happen in peak hour traffic or 20km from home or worse still - when I'm turning across oncoming traffic BANG.

In the meantime - out with the mutimeter tomorrow AGAIN

[eurisko]

Have you done a fault code check?

Bridge the diagnostic connector and see the flashes on the ECM light for the code... probably the best, and fastest way to fault find.... much better than running around in Field Test mode....

[ffourc]

re: your post Eurisko, to run in field test mode, I need to bridge the diagnostic plug [i've installed a simple push on/off switch...so easy now]- then start/drive the car - so yes I've checked for codes - and I'm not pulling any*

codes are only generated when a sensor fails, or an extreme(low or high,time) voltage is registered, this doesn't occur in many situations unfortunately. I could list problems I've fixed in my and my "friend's" cars, that were all ECCS related and significant , but no (or wrong)codes were thrown to make my life easier.

*pulled a 45 (rich exhaust) 32or33 (afm) and 23 (no start signal) the other night - but unfortunately they're probably all related to the fact car was 'stalling' while still moving. the only code remaining when I rechecked the next day was 23(= jump start) I got excited when the ecm light came on (it hadn't previously, only code I was getting was 12!!!no problems detected) thinking the answer was at hand, but alas that wasn't the case.

and it isn't a ecm issue ( I've got a spare) or dizzy (as of last week I've got a spare)