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  #16  
Old 10-08-2016, 11:23 PM
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I want to update this old thread. It wasn't the PCM. It was after a session with a very good tech and multiple diagnostic tools was intermittent loss of 5 volt reference voltage. Tightened those pins there are two and it has been symptom free now for over 1000 miles.
 
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Old 10-09-2016, 09:43 AM
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Originally Posted by wtroger
I want to update this old thread. It wasn't the PCM. It was after a session with a very good tech and multiple diagnostic tools was intermittent loss of 5 volt reference voltage. Tightened those pins there are two and it has been symptom free now for over 1000 miles.
What pins are you referring to? On a sensor? Or on the PCM plug?
 
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Old 10-09-2016, 04:51 PM
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Originally Posted by F150Torqued
The negative fuel trims on both banks makes sense, given the reported misfires. (The unburned fuel reaches the upstream O2 sensors and they register "rich" condition to the PCM,

Being brought up on carburetors, I understand your thinking on this, but here's what happens:


Upon misfire, the O2 sensors don't sense unburned fuel. They sense the excess oxygen due to the misfire. (They are, in fact, "oxygen" sensors.)
If a slight misfire, the excess oxygen causes the PCM to add fuel to compensate for the perceived lean condition.


If the misfire becomes more severe, the PCM cuts back the fuel supply to the misfiring cylinder to protect the catalytic converter
 
  #19  
Old 10-09-2016, 05:08 PM
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Originally Posted by wtroger
From reading Ford documentation the CPS is only used once during a drive cycle and that is at start up.

Actually, at start up, the PCM uses the CKP to figure out which cylinder to fire. Lets say, as the starter cranks the engine over, the CKP signals cylinder #1 is approaching TDC. That's not enough information for the PCM to fire the #1 spark plug, because it doesn't know if cylinder #1 is on compression or exhaust. That's why it needs the CMP at start up (to determine which stroke #1 is on, and which injector to fire).


Once the engine gets started, the PCM can keep track of just where the crank is in its rotation and doesn't really need the CMP to keep running. Once the engine is running, if the CMP signal disappears the PCM can set the P0340, and the engine will keep running.
 
  #20  
Old 10-09-2016, 09:11 PM
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The loose pin(s) was in the connector attaching the the PCM. One can lose the 5 volt reference voltage by either a shorted sensor, loose pin, or bad wire. The loss of reference voltage cause the PCM to turn on codes for sensors that use it. That was the reason for a ton codes plus it causes the system to go dead rich. P2196 p2198
 
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Old 10-09-2016, 09:22 PM
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Originally Posted by wtroger
The loose pin(s) was in the connector attaching the the PCM. One can lose the 5 volt reference voltage by either a shorted sensor, loose pin, or bad wire. The loss of reference voltage cause the PCM to turn on codes for sensors that use it. That was the reason for a ton codes plus it causes the system to go dead rich. P2196 p2198
Thanks for the info. The PCM creates the 5 volt reference (it is feed with 12V). The 5V is then sent to some sensors which require power (e.g., MAF).
You don't happen to know the pin numbers which were problematic?
 
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