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Triggering a PICO recording with a scan tool
Posted to Technical Tips Forum on 8/9/2015 22 Replies

The other day, I had a 2015 F150 3.5L GTDI with a complaint of a CEL. It was setting the following DTCs:

P0365:00-28- (PCM) - (CMP) Sensor B Circuit (Bank 1) P0369:00-28- (PCM) - (CMP) Sensor B Circuit Intermittent (Bank 1)

After clearing the DTCs, I found it quite difficult to get the DTCs to return. I was finally able to figure out that if I allowed the engine to idle long enough, the CMP1_EXH Fault PID would randomly read "Yes":

2015 Ford F-150 Platinum, ECM/Inputs/Outputs Scan Data

Figuring out the cause wasn't that hard. Another tech suggested I swap the Intake and Exhaust CMP sensors and see if the fault followed (fortunately, the sensors are the same). The fault did follow the sensor:

2015 Ford F-150 Platinum, ECM/Inputs/Outputs Scan Data

A scope wasn't needed to diagnose this, but I still wanted to get a waveform of the fault just to see electrically what was going on. The problem with that was the engine might have to idle for up to 2 hours before it would happen. I had IDS set up to "Beep" and trigger a recording when the CMP1_EXH Fault PID changed to "Yes". My next goal was figure out someway to trigger a scope recording at the same time.

To do that, I connected an extra channel on the scope to the computer audio circuit using a line in cord plugged into the headphone jack. I then set up a Single trigger on that channel with trigger placed about midway in the time base. Now, when IDS triggered the recording and "Beeped", the voltage on the audio circuit would trigger, allow the waveform to fill the buffer, and stop the scope. I was now able to walk off and do something else.

Here's what I found:

2015 Ford F-150 Platinum, ECM/Inputs/Outputs Waveform

Here it is zoomed in:

2015 Ford F-150 Platinum, ECM/Inputs/Outputs Waveform

At first glance, those spikes on channel B look like ignition, but it's not.

On a side note, I used one computer for IDS and another computer for PICO. Here's a good post explaining why:

Robby from Alabama

Files Referenced:

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