04-21-2012 06:37 PM
Good day. Got following warnings on Cat CCM PC:
- High air filter restriction warning
- High air restriction derate
The atmospheric pressure sensor (right) supplies altitude information to the engine ECM along with calculated gauge pressure for all the engine pressure sensors. If the signal from the atmospheric pressure sensor is lost, an electronic derate may be initiated.
The turbocharger inlet pressure sensor (left) measures the inlet air pressure at the turbocharger compressor housing. The engine ECM uses the turbocharger inlet pressure sensor in combination with the atmospheric pressure sensor to determine air filter restriction.
The inlet air restriction is the pressure difference between the turbocharger inlet pressure sensor and the atmospheric pressure sensor. As the inlet air restriction increases, the pressure difference will increase and the ECM may initiate an air restriction event. In addition, the ECM will inform the monitoring system of the filter restriction.
We tried to replace both sensors, bu that didn't help. After engine restart "Peak air filter" parameter on Cat CCM PC increases little by little (may take between few hours to couple days) to ~15kPa and is not going down till engine is restarted. Engine keeps running under load without any problem.
What could be the cause of such kind of warnings?
04-22-2012 03:50 PM
Before and after replacing the sensors was a sensor calibration performed? Has to be done using CAT ET.
Usually if both sides are giving you a fault the atmospheric sensor is the likely culprit. Could also be a a wiring or connection problem. A quick check, wire a 10k ohm pot like shown in the Troubleshooting guide and install it in place of the sensor, if the signal stays stable it's proably the sensor, if not the wiring or even the ECM, but you'll have to work thru the circuit from the device connection back to the control.
Hope that helps, Mike L.
04-26-2012 02:51 AM
Great thanks for your reply. No, we didn't make calibration. But the thing that we did:
Let's assume, we have engine #1 - with problem and engine #2 - without air restriction problem.
We installed new (uncalibrated) sensors on engine #1 and got alarm. We removed sensors from engine #1 and installed them on engine #2, sensors from engine #2 we installed on engine #1. And still got alarm on engine #1, as before. Engine #2 is running with new (uncalibrated) sensors without any warninigs/faults.
Regarding 10k ohm pot - will try, thanks for the idea.
05-08-2012 10:32 PM
Maybe I should clarify this a bit, the term "calibration" in this sense is not accurate, the ECM compensates the inputs from the other pressure sensors to read what the atmospheric reads, this accounts for not only differences in the sensor output, but also lead resisitnace, power supply variations and variations in the analog inputs. This "calibration" is done with engine off and basically sets all sensor readings in the ECM to match the atmospheric sensor.
So it is quite common to pull off a supposed "bad" sensor from one engine and have it work on another without calibration, as long as it ends up close the what the ECm thinks the atmo sensor is reading.
Ideally to best troubleshoot this use CAT ET and in Status pull up all the pressure sensors to read in atmospheric values, remember the one you can't change is the atmo sensor, it needs to read 14.6 PSIA at sea level, when you perform the calibration, the other readings will normalize to that reference. Then turn off the battery, let it sit powered down for about 10 minutes, then bring it back up and go back into ET, all the sensors should still read atmospheric pressure within 0.1 psi.
Hope that helps, Mike L.
05-17-2012 07:50 AM
Are we talking about a series 1 or 2 engine. the difference:
the wiring boom of the series 1 is soft. series 2 is ridgid. also series 1 has a big dashboard with plenty gauges and series 2 has only the marine power display.
be aware that in case of the series 2 3500, there is a fault in the MPD panel. the restriction value and alarming is reversed by accident. left indication is right and for right side its left. Most of the times is the atmospheric pressure has a fault youll see it first on the crankcase pressure.
but the series 2 has a notorious problem with the connectors which vibrate too much beter is to order a new type with a integrated piece of wiring.
for air filter/atmospheric and crankcase pressure: 304-5666.
for boost pressure: 304-5667
for oil and fuel pressure: 304-5668.
for my opinion with this new sensors there is hardly any problems.