Re: PCM question
[Re: cudaman1969]
#3092498
11/08/22 08:58 AM
11/08/22 08:58 AM
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Joined: May 2003
Posts: 3,018 N.W. Florida
Fat_Mike
master
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master
Joined: May 2003
Posts: 3,018
N.W. Florida
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Bad ECT Sensor?
From the 2001 Service manual:
ENGINE COOLANT TEMP SENSOR - 3.9L/5.2L/5.9L DESCRIPTION The Engine Coolant Temperature (ECT) sensor is used to sense engine coolant temperature. The sensor protrudes into an engine water jacket. The ECT sensor is a two-wire Negative Thermal Coefficient (NTC) sensor. Meaning, as engine coolant temperature increases, resistance (voltage) in the sensor decreases. As temperature decreases, resistance (voltage) in the sensor increases. OPERATION At key-on, the Powertrain Control Module (PCM) sends out a regulated 5 volt signal to the ECT sensor. The PCM then monitors the signal as it passes through the ECT sensor to the sensor ground (sensor return). When the engine is cold, the PCM will operate in Open Loop cycle. It will demand slightly richer airfuel mixtures and higher idle speeds. This is done until normal operating temperatures are reached. The PCM uses inputs from the ECT sensor for the following calculations: • for engine coolant temperature gauge operation through CCD or PCI (J1850) communications • Injector pulse-width • Spark-advance curves • ASD relay shut-down times • Idle Air Control (IAC) motor key-on steps • Pulse-width prime-shot during cranking • O2 sensor closed loop times • Purge solenoid on/off times • EGR solenoid on/off times (if equipped) • Leak Detection Pump operation (if equipped) • Radiator fan relay on/off times (if equipped) • Target idle speed REMOVAL WARNING: HOT, PRESSURIZED COOLANT CAN CAUSE INJURY BY SCALDING. COOLING SYSTEM MUST BE PARTIALLY DRAINED BEFORE REMOVING THE COOLANT TEMPERATURE SENSOR. REFER TO GROUP 7, COOLING. (1) Partially drain cooling system (Refer to 7 - COOLING - STANDARD PROCEDURE). (2) Remove air cleaner assembly. (3) Disconnect electrical connector from sensor (Fig. 14). (4) Engines with air conditioning: When removing the connector from sensor, do not pull directly on wiring harness. Fabricate an L-shaped hook tool from a coat hanger (approximately eight inches long). Place the hook part of tool under the connector for removal. The connector is snapped onto the sensor. It is not equipped with a lock type tab. (5) Remove sensor from intake manifold. INSTALLATION (1) Install sensor. (2) Tighten to 6–8 N·m (55–75 in. lbs.) torque. (3) Connect electrical connector to sensor. The sensor connector is symmetrical (not indexed). It can be installed to the sensor in either direction. (4) Install air cleaner assembly. (5) Refill cooling system (Refer to 7 - COOLING - STANDARD PROCEDURE).
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Re: PCM question
[Re: Fat_Mike]
#3092507
11/08/22 09:27 AM
11/08/22 09:27 AM
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Joined: Jan 2004
Posts: 8,192 fredericksburg,va
cudaman1969
OP
master
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OP
master
Joined: Jan 2004
Posts: 8,192
fredericksburg,va
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Bad ECT Sensor?
From the 2001 Service manual:
ENGINE COOLANT TEMP SENSOR - 3.9L/5.2L/5.9L DESCRIPTION The Engine Coolant Temperature (ECT) sensor is used to sense engine coolant temperature. The sensor protrudes into an engine water jacket. The ECT sensor is a two-wire Negative Thermal Coefficient (NTC) sensor. Meaning, as engine coolant temperature increases, resistance (voltage) in the sensor decreases. As temperature decreases, resistance (voltage) in the sensor increases. OPERATION At key-on, the Powertrain Control Module (PCM) sends out a regulated 5 volt signal to the ECT sensor. The PCM then monitors the signal as it passes through the ECT sensor to the sensor ground (sensor return). When the engine is cold, the PCM will operate in Open Loop cycle. It will demand slightly richer airfuel mixtures and higher idle speeds. This is done until normal operating temperatures are reached. The PCM uses inputs from the ECT sensor for the following calculations: • for engine coolant temperature gauge operation through CCD or PCI (J1850) communications • Injector pulse-width • Spark-advance curves • ASD relay shut-down times • Idle Air Control (IAC) motor key-on steps • Pulse-width prime-shot during cranking • O2 sensor closed loop times • Purge solenoid on/off times • EGR solenoid on/off times (if equipped) • Leak Detection Pump operation (if equipped) • Radiator fan relay on/off times (if equipped) • Target idle speed REMOVAL WARNING: HOT, PRESSURIZED COOLANT CAN CAUSE INJURY BY SCALDING. COOLING SYSTEM MUST BE PARTIALLY DRAINED BEFORE REMOVING THE COOLANT TEMPERATURE SENSOR. REFER TO GROUP 7, COOLING. (1) Partially drain cooling system (Refer to 7 - COOLING - STANDARD PROCEDURE). (2) Remove air cleaner assembly. (3) Disconnect electrical connector from sensor (Fig. 14). (4) Engines with air conditioning: When removing the connector from sensor, do not pull directly on wiring harness. Fabricate an L-shaped hook tool from a coat hanger (approximately eight inches long). Place the hook part of tool under the connector for removal. The connector is snapped onto the sensor. It is not equipped with a lock type tab. (5) Remove sensor from intake manifold. INSTALLATION (1) Install sensor. (2) Tighten to 6–8 N·m (55–75 in. lbs.) torque. (3) Connect electrical connector to sensor. The sensor connector is symmetrical (not indexed). It can be installed to the sensor in either direction. (4) Install air cleaner assembly. (5) Refill cooling system (Refer to 7 - COOLING - STANDARD PROCEDURE). If bad would it still show the temp on the gauge in cluster?
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Re: PCM question
[Re: cudaman1969]
#3092512
11/08/22 09:53 AM
11/08/22 09:53 AM
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Joined: Aug 2011
Posts: 2,842 Pattison Texas
CSK
master
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master
Joined: Aug 2011
Posts: 2,842
Pattison Texas
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I have had slow,lazy o2 sensors do that, they look good on the scanner
1968 Charger COLD A/C Hilborn EFI 512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim 2020 T/A 392 Stock 11.79 @ 114.5
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Re: PCM question
[Re: cudaman1969]
#3092595
11/08/22 03:38 PM
11/08/22 03:38 PM
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Joined: Sep 2003
Posts: 19,239 north of coder
moparx
"Butt Crack Bob"
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"Butt Crack Bob"
Joined: Sep 2003
Posts: 19,239
north of coder
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i think the sender for the dash gauge is a separate one. i have seen where sender bulbs [the part that is in the coolant stream] turn "green" over time from [i think] lime deposits in the water used to top off, or refill the coolant system when changing out the mix. those "green" deposits actually insulate the bulb from reading the exact temperature. shining the bulb back to the original brass sometimes restores the sender's function. not saying it works 100% of the time, but it's well worth trying. just something i have had experience with, and it's results. your mileage will vary.
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Re: PCM question
[Re: cudaman1969]
#3092599
11/08/22 03:47 PM
11/08/22 03:47 PM
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Joined: May 2003
Posts: 3,018 N.W. Florida
Fat_Mike
master
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master
Joined: May 2003
Posts: 3,018
N.W. Florida
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If bad would it still show the temp on the gauge in cluster? hmmm...probably not. Long story short, I was thinking the gauge read directly from the coolant temperature sending unit. After doing more reading it looks like the gauge gets its input from the PCM, which it gets from the ECT. I wish I had a way to send this FSM to you...
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Re: PCM question
[Re: cudaman1969]
#3092642
11/08/22 06:23 PM
11/08/22 06:23 PM
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Joined: Oct 2005
Posts: 4,935 WI
Dcuda69
master
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master
Joined: Oct 2005
Posts: 4,935
WI
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Why would my Ram Van not be going into closed loop, oxygen sensors are both working. Long term shows rich all the time, temp is 199. 12.1 mpg at any speed. Some more info might help us help you. When you say no closed loop....your scan tool shows open loop? O2 sensors working...all of them and what are the readings? Long term shows rich? What exactly is it showing and what is short term? Have all the monitors ran and passed? Any codes/pending codes? Any running concerns(besides mpg)? Have you looked at generic data in OBDII or just vehicle specific? Have you checked fuel pressure? Just some quick things that come to mind. Good luck!
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