Follow these procedures to diagnose and correct Camshaft Position Sensor (CMP) faults.
Section 19.1.1
Signal Functions
The CMP sensor is a Hall Effect type sensor that generates a digital frequency as windows on the timing disk pass through its magnetic field. The frequency of the windows passing by the sensor as well as the width of selected windows allow the ECM to detect engine speed and position. See Figure
“Camshaft Position Sensor Functions”
.
Figure 1. Camshaft Position Sensor Functions
- Engine Speed — Determined by counting 24 windows on the timing sensor disk each camshaft revolution.
- Fuel Timing Control — the position of the cylinder No. 1 is determined by distinguishing a narrow vane on the camshaft timing sensor disk.
- Engine Mode Selection — Allows the ECM to discern when the engine is in the OFF, crank or run mode.
- Injection Control Pressure — Engine speed is one of the controlling variables in the calculation of desired injection control pressure.
- Fuel Quantity Control/ Torque Limiting — Engine torque and fuel is controlled and is dependent on engine speed. Fuel quantity is determined by engine speed.
Section 19.1.2
Fault Detection / Management
An inactive CMP signal during cranking is detectable by the ECM. An inactive CMP signal will cause a no start condition. Electrical noise can also be detected by the ECM; if the level is sufficient to affect engine operation a corresponding fault code will be set. The engine will not operate without a functioning CMP signal. See Figure
“Camshaft Position Sensor”
.
Figure 2. Camshaft Position Sensor
Connector voltage checks are listed in Table
“Connector Voltage Checks”
. These checks are performed with the sensor connector disconnected, the ignition key ON and all accessories OFF.
| Test Points | Spec. | Comments |
| A to Grd. | 0 volts | No voltage expected. |
| B to Grd. | 5 ± 5 volts | VREF, check key ON, VREF not present check open/short to ground No. 40 to B, see VREF circuit |
| C to Grd. | 5 ± 5 volts | If < 4.5v check for poor connection; if 0v check for open/short to ground circuit. |
Connector checks to chassis ground are listed in Table
“Connector Checks to Chassis Ground”
. These checks are performed with the sensor connector (406) 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, > 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”
. These checks are performed with the breakout box installed on the engine harness only, and ignition key OFF.
| Test Points | Spec. | Comments |
| #53 to A | < 5 Ω | Resistance from harness connector to 60-pin connector – Signal grd has dedicated ground ckt. |
| #40 to B | < 5 Ω | Resistance from harness connector to 60-pin connector – VREF |
| #51 to C | < 5 Ω | Resistance from harness connector to 60-pin connector – CMP signal |
Operational voltage checks are listed in Table
“Operational Voltage Checks”
. These checks are performed with the breakout box installed in line with the ECM and the ignition key ON.
| Test Points
(+) #51 to (−) #53 |
Voltage Checks | |
| Voltage | Position | Comments |
| 5 ± .5v | Vane | With the breakout box installed, the CMP sensor and ECM connected, bar engine by hand. |
| .2 to 2v | Window | The CMP signal voltage should change voltage state as timing wheel on cam is rotated. |
Fault Code descriptions are listed in Table
“Fault Code Descriptions”
.
| Flash Code | Descriptions |
| 143 | Incorrect number of sync to transition counts detected; possible intermittent CMP sensor/circuit fault. |
| 144 | Electrical noise detected; check wire routing and grounds. |
| 145 | Inactive CMP signal detected during engine cranking when ICP pressure was sufficient for starting. |
| 612 | ECM/target disk mismatch detected (wrong ECM Programming/Installed). |
| 315 | Engine RPM exceeded 3,000 RPM. |
Section 19.1.3
Function of the Extended System
The Series 40E engine control system includes a CMP. This sensor provides the ECM with a signal that indicates camshaft position and engine speed.
The CMP sensor signal is used by the ECM to synchronize piston position to injector firing sequence. The injector firing order sequence begins when the ECM detects the narrow vane on the timing disk indicating No. 1 cylinder. Engine position for each cylinder is then continuously calculated as each vane on the timing disk passes by the CMP sensor. This information is processed by the ECM and used for injection timing and fuel delivery control. The ECM can then initiate the beginning of firing.
Section 19.1.4
Operation
The CMP is a Hall Effect type sensor that generates a digital frequency as windows on the timing disk pass through its magnetic field. The frequency of the windows passing by the sensor as well as the width of selected windows allow the ECM to detect engine speed and position. When the narrow vane passes the CMP, the signal on time is less than when the other vanes pass the sensor. This produces a signal that the ECM uses to indicate engine position.
Engine speed is detected by the ECM by counting the frequency of the 24 signal pulses for each camshaft revolution.
Section 19.1.5
ECM Diagnostics
Once the ECM has recognized the narrow vane (wide window) it will synchronize the engine firing order to the timing of the CMP signal. Every two crankshaft revolutions, it will verify that synchronization. If the ECM receives too many or too few pulses for the number of engine revolutions, it will set a fault code.
The engine will not operate without a functioning CMP signal. However, the ECM will attempt to determine the cause of an invalid signal and identify it with a fault code.
CMP codes that are set will become inactive codes if the key is turned off. These codes can be retrieved using the Self Test Input (STI) switch located on the vehicle dashboard or the EST (electronic service tool).
Section 19.1.6
Flash Codes
Several flash codes are connected to the CMP diagnostics:
Section 19.1.6.1
Flash Code 143
ATA code SID 21 FMI 2
Wrong number of CMP signal transitions per camshaft revolution.
Flash Code 143 indicates the ECM has received CMP signals with the wrong number of transitions. This indicates that the ECM has counted the voltage transitions and found less than the specified number of pulses from the sensor. When this problem is continuous, the engine will stop running and the ECM will log an active code. If the key is shut off, the code will become an inactive code. This code will not turn the warning light on.
Possible causes for code 143: Intermittent CMP signal caused by an intermittent circuit, defective CMP sensor, or incorrect CMP sensor to timing disk clearance.
Section 19.1.6.2
Flash Code 144
ATA code SID 21 FMI 2
CMP signal noise detected.
Flash Code 144 indicates that the ECM has detected voltage spikes or transitions other than the CMP signal. If this problem is continuous, the engine could stop running and the ECM will log an active code. If the key is shut off, the code will become an inactive code. This code will not cause the warning light to illuminate.
Flash Code 144 may be due to poor ground connections for CMP or other electronic components; wire harness shielding missing or incorrectly installed on the engine harness; or outside components that could induce voltage signals.
Section 19.1.6.3
Flash Code 145
ATA code SID 21 FMI 12
CMP signal inactive while ICP has increased.
Flash Code 145 indicates that the ECM does not detect a CMP signal. This code would set if the engine was rotating and the ECM detected a rise in ICP pressure, but did not detect a CMP signal. To set this code, the engine must be rotated long enough for the ICP to increase. When this code is set, the engine will not operate. This code will not cause the warning light to illuminate.
Possible causes for flash code 145: defective CMP sensor; faulty sensor circuitry; or improper air gap between sensor and camshaft timing disk.
Section 19.1.6.4
Flash Code 612
ATA code SID 21 FMI 7
Incorrect ECM installed for CMP timing disk.
Flash Code 612 indicates that the ECM has monitored the CMP signal and the signal is incorrect for the programming in the ECM. This means that the ECM does not recognize the signal generated from the timing disk and CMP sensor.
Possible causes: ECM has been accidently replaced with an incorrect ECM for the particular engine application; incorrect signal due to a defective CMP sensor or incorrect air gap between the CMP sensor and the timing disk.
Section 19.1.6.5
Flash Code 315
ATA code PID 190 FMI 0
Engine speed above warning level.
Flash Code 315 indicates that the ECM has detected an engine speed above 3,000 r/min. The most likely cause of the excessive engine speed is an unintended downshift, steep acceleration down a hill without correct brake application, or an external fuel source being ingested into the air intake system. The engine hours and miles of the last two over speed occurrences will be recorded in the Engine Event Log. Code 315 will cause the WARN lamp to illuminate.
| Series 40E Troubleshooting Manual – 6SE241 |
| Generated on 10-13-2008 |