The Engine Oil Pressure (EOP) sensor is a variable capacitance sensor, that when supplied with a 5 volt reference signal from the ECM, produces a linear analog voltage signal that indicates engine oil pressure. For the EOP sensor function diagram, see Figure
“Engine Oil Pressure Sensor Function Diagram”
.
Figure 1. Engine Oil Pressure Sensor Function Diagram
Engine Warning and Protection — An optional feature that, when enabled, will warn the driver of low engine oil pressure condition and can be programmed to shut the engine down.
Instrument Cluster Display — The ECM transmits sensed engine oil pressure information on the ATA data link that is for display on the instrument cluster.
Section 28.1.1
Fault Detection / Management
An EOP signal that is detected out of range high or low by the ECM will cause the engine to ignore the EOP signal and disable Engine Warning and Protection. For details of the engine oil pressure sensor, see Figure
“Engine Oil Pressure Sensor “
.
Figure 2. Engine Oil Pressure Sensor
Connector voltage checks are listed in Table
“Connector Voltage Checks”
. Checks are made with the sensor connector disconnected and the ignition key ON.
| Test Points | Spec | Comments |
| A to Grd | 0 volts | Signal ground; no voltage expected. |
| B to Grd | 5 volts ± .5 | VREF check with key ON; if voltage not in spec, see VREF circuit. |
| C to Grd | < .75 volts | If greater than 0.75 volts, signal ground wire is shorted to VREF or battery. |
Connector checks to chassis ground are listed in Table
“Connector Checks to Chassis Ground”
. Checks are made with the sensor connector disconnected, the positive battery cable disconnected, and the ignition key OFF.
| Test Points | Spec | Comments |
| A to Grd | < 5 Ω | Resistance to chassis ground, check with key OFF; if > 5 Ω, the harness is open. |
| B to Grd | > 1,000 Ω | Resistance less than 1,000 Ω indicates a short to ground. |
| C to Grd | > 1,000 Ω | Resistance less than 1,000 Ω indicates a short to ground. |
Harness resistance checks are listed in Table
“Harness Resistance Checks”
. Checks are made with the breakout box installed on the engine harness only.
| Test Points | Spec | Comments |
| #19 to A | < 5 Ω | Resistance from sensor connector to 60-pin connector – Signal ground. |
| #40 to B | < 5 Ω | Resistance from sensor connector to 60-pin connector – VREF. |
| #14 to C | < 5 Ω | Resistance from sensor connector to 60-pin connector – EOP signal. |
Operational signal checks are listed in Table
“Operational Signal Checks”
. Checks are made with the breakout box installed in line with the ECM.
| Test Points
(+) #14 to (-) #19 |
Operational Signal Checks
Check with breakout box installed in line w/ECM |
||
| Voltage | PSIG | kPa | Comments |
| .89v | 5 | 34 | Pressure will vary with engine speed and temperature. |
| 1.15v | 10 | 69 | |
| 2.40v | 35 | 241 | |
| 3.61v | 60 | 414 | |
Fault code descriptions are listed in Table
“Fault Code Descriptions”
.
| Circuit Faults | Description |
| 211 | Signal was less than .039 volts for more than 0.1 seconds. |
| 212 | Signal voltage was greater than 4.9 volts for more than 0.1 seconds. |
| 225 | Engine oil pressure was sensed greater than 40 psi with the ignition key ON, engine OFF. |
| Oil Pressure Faults | Description |
| 313 | Engine oil pressure < 5 psi (34 kPa) @ 700 r/min or 10 psi (69 kPa) @ 1400 r/min or 20 psi (138 kPa) @ 2,000 r/min. |
| 314 | Engine oil pressure < 2 psi (14 kPa) @ 700 r/min or 5 psi (34 kPa) @ 1,400 r//min or 12 psi (152 kPa) @ 2,000 r/min. |
Section 28.1.2
Function
The Engine Oil Pressure sensor (EOP) is standard in the engine control system. Engine shutdown and protection is an option that can be ordered with the vehicle or activated at the dealer.
The ECM measures the EOP signal to monitor the oil pressure during engine operation. If the oil pressure drops below 5.0 psi (34 kPa) @ 700 r/min or 10.0 psi (69 kPa) @ 1,400 r/min or 20.0 psi (138 kPa) @ 2,000 r/min, the ECM will illuminate the OWL (oil/water light) and sound the audible warning alarm. If the vehicle is equipped with the Engine Shutdown system and the oil pressure drops to 2.0 psi (14 kPa) @ 700 r/min or 5.0 psi (34 kPa) @ 1,400 r/min or 12.0 psi (152 kPa) @ 2,000 r/min, the ECM will shut the engine OFF.
Section 28.1.3
Operation
The EOP sensor is a variable capacitance sensor. When pressure is applied to the sensor, the capacitance changes in relation to the pressure.
The ECM supplies a regulated 5 volt signal to terminal B of the EOP sensor from terminal 40 of the ECM. The EOP sensor is supplied a signal return (ground) at terminal A to terminal 19 of the ECM.
During engine operation, oil pressure acting on the sensor causes the sensor’s capacitance to vary which changes the incoming 5 volt reference signal in relation to pressure. The sensor’s oil pressure signal at terminal C is sent to terminal 14 of the ECM. This signal increases equally in proportion to an increase in pressure up to a maximum of 85.3 psi (588 kPa).
Section 28.1.4
ECM Diagnostics
The ECM continuously monitors the signal from the EOP sensor to ensure the signal is within the correct operating range. If the signal is lower or higher than required, the ECM will set a fault code. This fault code is retrieved using the EST or by reading the flash code using the STI diagnostic switch. If the ignition key is shut off, the code will be stored as an inactive code.
During engine operation, the ECM also monitors the engine speed signal. It compares the expected oil pressure specification versus engine speed. If the ECM detects that the oil pressure is lower for a given engine speed the ECM will set a fault code. If the pressure is lower than the critical level, the ECM will automatically record this as a low oil pressure “Event” that is stored in the ECM memory and cannot be erased using the EST. This becomes a record of operation of the engine.
Section 28.1.5
Flash Codes
The following fault codes could result form troubleshooting the EOP:
Section 28.1.5.1
Flash Code 211
ATA Code PID 100 FMI 4
Engine oil pressure signal out of range LOW.
An out of range LOW code will be set if the ECM detects a voltage less than .039 volts for more than 0.1 seconds. If this fault code is set, the ECM will ignore the EOP signal and continue to operate normally. However, if the fault is Active, the ECM will turn on the Engine Warning light.
Flash Code 211 may be caused by an open VREF feed, open signal circuit, or a defective sensor.
Section 28.1.5.2
Flash Code 212
ATA Code PID 100 FMI 3
Engine oil pressure signal out of range HIGH.
An out of range HIGH code will be set if the ECM detects a voltage more than 4.9 volts for more than 0.1 seconds. If this fault code is set, the ECM will ignore the EOP signal and continue to operate normally. If this fault is active, the ECM will illuminate the Engine Warning light.
Flash Code 212 may be caused by an open signal return circuit, a short to a voltage source, or a defective sensor.
Section 28.1.5.3
Flash Code 225
ATA Code PID 100 FMI 0
Engine oil pressure sensor signal in range fault.
Flash Code 225 will be set by the ECM if the signal from the EOP sensor is higher than expected with the key ON and the engine OFF (a signal that indicates 40 psi). If the ECM detects this fault, it will ignore the EOP signal and illuminate the Engine Warning lamp. This code most likely will be set because of a defective EOP sensor or a biased circuit.
Section 28.1.5.4
Flash Code 313
ATA Code PID 100 FMI 1
Engine oil pressure below warning level.
Flash Code 313 indicates that the oil pressure has dropped below the warning level. The specification for the warning level is 5.0 psi (34 kPa) @ 700 r/min or 10.0 psi (69 kPa) @ 1,400 r/min or 20.0 psi (138 kPa) @ 2,000 r/min.
Flash Code 313 may be caused by a defective sensor sending an incorrect signal. To confirm this, compare actual oil pressure (with a mechanical gauge) to the reading on the data list of the EST. Low oil pressure due to defective mechanical components will also set this code.
Note: It may be possible to set this code at start up, especially if the oil was just changed, or after a rebuild until the oil system is primed.
Section 28.1.5.5
Flash Code 314
ATA Code PID 100 FMI 7
If Flash Code 314 is set, the oil pressure has dropped below the critical level. The specification for the critical level is 2.0 psi (14 kPa) @ 700 r/min or 5.0 psi (34 kPa) @ 1,400 r/min or 22.0 psi (152 kPa) @ 2,000 r/min.
Flash Code 314 may be caused by a defective sensor sending an incorrect signal. To confirm this, compare the actual oil pressure with a mechanical gauge installed, to the reading on the data list of the EST. Low oil pressure due to defective mechanical components will also set this code.
| Series 40E Troubleshooting Manual – 6SE241 |
| Generated on 10-13-2008 |