Cummins ISB4.5 CM2150 Fault Code: 2973 PID: 106 SPN: 102 FMI: 2 Intake Manifold 1 Pressure – Data Erratic, Intermittent, or Incorrect.

Circuit Description
The engine control module (ECM) provides a 5 volt supply to the intake manifold pressure sensor on the sensor supply circuit. The ECM also provides a ground on the sensor return circuit. The intake manifold pressure sensor provides a signal to the ECM on the intake manifold pressure sensor signal circuit. This sensor signal voltage changes, based on the pressure in the intake manifold.

Component Location
The intake manifold pressure/temperature 1 sensor is located in the air intake manifold.

The barometric pressure sensor can be externally mounted on the engine or can be an internal component within the ECM. Check engine wiring diagram for circuit details.

Conditions for Running the Diagnostics
This ECM diagnostic runs in two parts consisting of three separate conditions without keying off between steps:

1. Key ON – Part 1 of this diagnostic runs a sensor rationality check when the keyswitch is initially turned on. If the fault code became active at key ON only, it has failed the first check.

2. Operation – Part 2 of this diagnostic will run a pressure rationality check when the engine is running under normal conditions. The diagnostic runs a check at the following conditions:

>1500 rpm at 100 percent load, for 25 non-consecutive seconds.
<2000 rpm while motoring for 25 non-consecutive seconds with a charge-air pressure < 140kPa or 150kPa depending upon the specific ECM calibration. Exhaust brake must be disabled at all times or the diagnostic will not run. Service tips: -If the key ON has malfunctioned, only the key ON rationality needs to be run. -If the fault code became active at >1500 rpm and under load, only the >1500 rpm condition needs to be completed.
-If the fault code became active at <2000 rpm while motoring, only the <2000 rpm motoring condition needs to be completed. Check the ECM job image and fault code snapshot window in INSITE™ electronic service tool to see if the fault code flagged while the engine was running or at key ON. Check the load or motoring condition to help determine which part malfunctioned. Conditions for Setting the Fault Codes This diagnostic checks the value of the intake manifold pressure sensor at key ON and while the engine is running. If the value of the intake manifold pressure is not reading ambient pressure at key ON or is higher or lower than expected during normal engine operation, this fault code is logged. Action Taken When the Fault Code is Active -The ECM illuminates the MIL immediately when the diagnostic runs and fails ONE trip. -A significant engine de-rate will occur immediately to default OFC fuelling tables to protect the engine from damage. Conditions for Clearing the Fault Code -Run the ECM diagnostic as described above. -Once the diagnostic has completed, the fault code will go inactive if it passes. -As soon as the diagnostic has completed and passed one trip, the MIL will go out immediately. -Once the fault code is inactive, use the “clear all faults” command from the latest version of INSITE™ electronic service tool. Shop Talk This diagnostic consists of two parts. At key ON, before the engine starts, the sensor readings for intake manifold pressure, barometric air pressure, and exhaust gas pressure are compared to each other. This fault code occurs if the intake manifold pressure sensor reading is different from the other sensor readings. This check is only done once after the keyswitch is turned ON. This fault can also be set active when the intake manifold pressure is too high or low for the present engine operating conditions when the engine is running. The ECM compares the intake manifold pressure reading to turbocharger speed to determine if the pressure reading is valid. Possible Causes -A damaged intake manifold pressure sensor -A damaged barometric pressure sensor -Leaks in the air intake system between the turbocharger and intake manifold -Restriction in the charge-air cooler -A damaged turbocharger speed sensor -A damaged turbocharger compressor intake temperature sensor -A damaged engine wiring harness can cause intermittent fault codes due to intermittent resistances. Check the wiring diagram for shared supply and return circuit on sensors. It is possible that more than one sensor could be reading incorrectly if a common supply/ground problem exists in the circuit. Use INSITE™ electronic service tool to log any fluctuation in sensor voltage/values when the harness is moved. NOTE: In the guided steps for Fault Code 2973, gauge pressure may need to be converted to absolute pressure, depending on the engine you are troubleshooting. Barometric pressure is approximately 29.92 in-Hg at sea level. (Absolute Pressure) The intake manifold pressure is approximately 0 in-Hg when the engine is not running. (Gauge Pressure) 29.92 in-Hg = 1 atmosphere = 1.013 bar Example: If the barometric (Absolute) pressure sensor reads 31 in-Hg and the intake manifold (Gauge) pressure reads -5 in-Hg then the difference can be calculated as follows: 1. Convert the intake manifold (Gauge) pressure to Absolute pressure = (-5 + 29) = 24 in-Hg. 2. Subtract the new 24 in-Hg value from the original barometric value of 31 in-Hg. (31 – 24) =7 3. The difference is 7 in-Hg. 7 in-Hg is greater than the specification of 3 in-Hg in the troubleshooting steps and will cause the fault to become active. 4. Use the Barometric Pressure at Altitude table in the following procedure to help understand ambient pressure at different altitudes.