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07:46:31 - 05/08/2024
Dakota Performance
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Bernd
GenIII
 
1/29/2001
08:54:47
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 Subject: Open/Closed Loop Operation
IP: Logged
Message:
A few people have asked about the O2 sensors and wide open throttle operation...so here's the facts on the OPEN/CLOSED Loop operation of our trucks:
There are 7 different modes (conditions) that are used (besides Key-ON and Key-Off mode) and here's the list of what sensors are monitors and determine the mode:
(1) Engine Start-Up Mode (OPEN LOOP)
Battery Voltage
Coolant Temp
Crank Position
Intake Air Temp
MAP
TPS
Starter Motor Relay
Cam Position
(2) Engine Warm-Up Mode (OPEN LOOP)
Battery Voltage
Coolant Temp
Crank Position
Intake Air Temp
MAP
TPS
Cam Position
Park/Neutral Safety Switch (Automatics Only)
(3) Idle mode (Once at Operating Temp: CLOSED LOOP)
A/C Select (if equipped)
A/C Request (if equipped)
Battery Voltage
Coolant Temp
Crank Position
Intake Air Temp
MAP
TPS
Cam Position
O2 Sensors
Park/Neutral Safety Switch (Automatics Only)
(4) Cruise Mode (CLOSED LOOP)
A/C Select (if equipped)
A/C Request (if equipped)
Battery Voltage
Coolant Temp
Crank Position
Intake Air Temp
MAP
TPS
Cam Position
O2 Sensors
Park/Neutral Safety Switch (Automatics Only)
(5) Acceleration Mode (OPEN LOOP)
A/C Select (if equipped)
A/C Request (if equipped)
Battery Voltage
Coolant Temp
Crank Position
Intake Air Temp
MAP
TPS
Cam Position
Vehicle Speed Sensor
Park/Neutral Safety Switch (Automatics Only)
(6) Deceleration Mode (OPEN LOOP)
A/C Select (if equipped)
A/C Request (if equipped)
Battery Voltage
Coolant Temp
Crank Position
Intake Air Temp
MAP
TPS
Cam Position
Park/Neutral Safety Switch (Automatics Only)
Vehicle Speed Sensor
(7) Wide Open Throttle - WOT (OPEN LOOP)
Battery Voltage
Coolant Temp
Crank Position
Intake Air Temp
MAP
TPS
Cam Position
Under conditions 1,2,4,5,6,7...the O2 Sensor is ignored by the PCM.
Yes, even in the FSM's..."During Open-Loop modes, the PCM receives input signals and responds according to preset PCM programming. Input from the O2 sensors is not monitored during Open-Loop modes."
Bernd D. Ratsch
1997 Dodge Dakota SLT
Supercharged w/Nitrous
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MARK A
Dodge Dakota
JOIN HERE
4/06/2002
11:09:36
| RE: Open/Closed Loop Operation
IP: Logged
Message:
ANY INFO ON THE SPARK CONTROL COMPUTER - 1986- 1987 TYPE ???????
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Duner
Dodge Dakota
JOIN HERE
4/06/2002
13:15:59
| RE: Open/Closed Loop Operation
IP: Logged
Message:
Slight oversight in the part about the O2 sensors... cruise mode (4) should be off your list of O2 sensor ignored modes by the PCM. Closed loop at Idle and Cruise (3 & 4). Open loop when engine is cold, accelerating or deccelerating.
My understanding is that the PCM looks for threshold values from the coolant temp sensor, TPS and MAP sensor to decide when it's in Open or Closed loop.
So in other words -
Cold Start
(1 & 2) Engine is cold (coolant temp sensor threshold) The PCM lets the engine run under preset fuel/timing curves until it's warmed up.
After the engine is warmed up
(3) At idle the PCM uses info from the O2 sensors to trim the injector pulse width to maintain proper A/F ratio for efficient and clean operation. The TPS sensor tells the PCM that it's supposed to be idling, so the PCM tries to maintain a target idle speed that's programmed in the PCM. If you turn on the A/C, the PCM tries to maintain a different target idle speed which is also programmed in the PCM.
(4) At cruise the PCM uses info from the O2 sensors to trim the injector pulse width to maintain proper A/F ratio for efficient and clean operation. As long as the MAP sensor and TPS sensors stay within a certain set of parameters, the PCM stays in closed loop.
(5 & 7) If you are accelerating, the PCM sees the drop in vaccuum from the MAP sensor and decides how hard you are trying to accelerate by info from the TPS. If the PCM sees values from both of these sensors that are above/below certain thresholds (low/no vaccum with added throttle), then the PCM goes into open loop. In open loop the PCM will ignore info from the O2 sensors. The PCM lets the engine run under preset fuel/timing curves that are based upon throttle position, RPMs and intake air temp readings.
(6) When you are deccelerating the PCM knows this because the TPS is at a lower setting than is necessary for that rpm and the MAP sensor is reading high vaccuum. The PCM will again go to the preset fuel/timing curves that are stored.
Again, If I have any of this wrong - somebody correct me. (nicely please?) hehehe
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yusri
Dodge Dakota
JOIN HERE
7/24/2004
11:49:26
| RE: Closed Loop Operation
IP: Logged
Message:
the example of control system related in mechatronics
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