Going from open loop to closed loop
Le Mans Master
Joined: Oct 2004
Posts: 6,314
Likes: 508
From: South-central Missouri
The primary criteria is coolant temperature and throttle position. And, certain operating faults will prevent Closed Loop operation.
The coolant temp threshold may vary a little with model year perhaps, but @ or about 140ºF will trigger the (ECM) to switch to closed loop. And, after that, throttle position threshold will result in the (ECM) to switch back to OPEN LOOP (as long as you have your foot "in it").
Some, through ignorance or by design, calibrate the tuning to keep it in OPEN LOOP at all times. Some track car applications may benefit from full time OPEN LOOP, but certainly not if the car is ever street driven.
Your FSM will provide more and specific details.
The coolant temp threshold may vary a little with model year perhaps, but @ or about 140ºF will trigger the (ECM) to switch to closed loop. And, after that, throttle position threshold will result in the (ECM) to switch back to OPEN LOOP (as long as you have your foot "in it").
Some, through ignorance or by design, calibrate the tuning to keep it in OPEN LOOP at all times. Some track car applications may benefit from full time OPEN LOOP, but certainly not if the car is ever street driven.
Your FSM will provide more and specific details.
Last edited by Paul Workman; Dec 3, 2014 at 01:42 AM.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
They may be slightly different for 1989, but these are the conditions for 1986 (same ECM):
Coolant temperature > 40.7°C = 104.4°F
Engine run time > 300 seconds (cold) if coolant temperature < 58.5°F
Engine run time > 206 seconds (warm) if coolant temperature > 58.5°F and < 158.5°F
Engine run time > 50 seconds (hot) if coolant temperature > 158.5°F
Oxygen sensor reading between 0.195 and 0.686 volts for > 10 seconds
The oxygen sensor takes quite a while to get hot enough to put out a valid reading. It will be the last item to meet the criteria above.
Coolant temperature > 40.7°C = 104.4°F
Engine run time > 300 seconds (cold) if coolant temperature < 58.5°F
Engine run time > 206 seconds (warm) if coolant temperature > 58.5°F and < 158.5°F
Engine run time > 50 seconds (hot) if coolant temperature > 158.5°F
Oxygen sensor reading between 0.195 and 0.686 volts for > 10 seconds
The oxygen sensor takes quite a while to get hot enough to put out a valid reading. It will be the last item to meet the criteria above.
Last edited by Cliff Harris; Dec 3, 2014 at 01:56 AM.
Thread Starter
Burning Brakes
Joined: Dec 2012
Posts: 788
Likes: 160
From: Rio Rico, AZ
I should be sleeping but the FSM for 1989 says the engine goes from open to closed after 40 degrees C (104 degrees F). Should have dug a bit deeper before bugging you guys.
Thanks, Went
Thanks, Went
