The ECM / IDM communication link consists of a series of interdependent signals that include the CKPO, CMPO, and the CAN 2 datalink.
The CKPO signal is a 0 V to 12 V signal that communicates (from ECM to IDM) the position of the crankshaft. The signal is used by the IDM to synchronize the injector firing sequence and is calculated from the signal generated from the CKP sensor.
The ECM generates the CKPO signal by pulling down (switching to ground) a 12 V communication circuit in the IDM.
The CMPO signal is a 0 V to 12 V signal that communicates (from ECM to IDM) the position of the camshaft. The signal is used by the IDM to synchronize the injector firing sequence and is calculated from the signal generated from the CMP sensor.
The ECM generates the CMPO signal by pulling down (switching to ground) a 12 V communication circuit in the IDM.
CAN 2 datalink is a J1939 high speed private communication datalink between the ECM, IDM, and EGR drive module. The ECM receives messages that include injector coil status, IDM calibration level, CMPO and CKPO DTCs, injector DTCs, IDM DTCs, and injector test results from the IDM. The IDM receives injector diagnostic commands, operation strategies, modes and conditions from the ECM.
NOTE: CAN 2 datalink is used only as communication between the ECM, IDM, and EGR drive module.
There is no relation to the CAN 1 datalink that is used for communication with various processors on a vehicle.
Fault Detection / Management
The ECM continuously monitors the IDM. When the ECM fails to receive required continuous communication from the IDM, the ECM will set a DTC.
ECM / IDM Diagnostic Trouble Codes (DTCs)
DTCs are read using the Electronic Service Tool (EST) or by counting the flashes from the amber and red ENGINE lamp.
DTC 543
ECM / IDM communications fault
• DTC 543 is set by the ECM when the ECM is not communicating with the IDM.
• DTC 543 can be set when CAN 2 datalink J1939 between ECM and IDM is shorted to ground, V REF, or battery or the circuit is open. If IDM power is low, DTC 543 can be set.
• When DTC 543 is active the amber ENGINE lamp is illuminated.
NOTE: If a no start condition exists with DTC 543 and 368 active, check the CAN 2 datalink wiring (EGR to ECM and IDM to ECM). See “EGR Actuator” (page 413) in this section. One of the CAN 2 datalink wires (CAN 2 positive or negative) is open, short to ground, or a short to power exists.
DTC 551
IDM / CMPO signal inactive
• DTC 551 is set by the ECM when no CMPO signal is present while the CKPO is active. DTC 551 can also be set when no CMPO/CKPO is present while the ECM reports it is in the run mode.
• DTC 551 can be set when the CMPO is open, shorted to ground, or shorted to a voltage source. DTC 551 can also be set if logic power is low.
DTC 552
IDM incorrect CMPO signal signature
• DTC 552 is set when the CMPO transition occurs at the wrong CKPO tooth.
• DTC 552 can be set due to electrical noise creating a miscount on CMP location.
DTC 553
IDM / CKPO signal inactive
• DTC 553 is set by the ECM when no CKPO signal is present while the CMPO is active. DTC 552 can also be set when no CMPO/CKPO is present while the ECM reports it is in the run mode.
• DTC 553 can be set when CKPO is open, shorted to ground, or shorted to a voltage source. DTC 553 can also be set if logic power is low.
DTC 554
IDM incorrect CKPO signal signature
• DTC 554 is set by the ECM when CKPO signal has too few or too many transitions per engine rotation.
• DTC 554 can be set due to electrical noise creating a miscount on CKP location.
Tools
• EST with MasterDiagnostics® software
• EZ-Tech® interface cable
• Digital Multimeter (DMM)
• Breakout Box
• Terminal Test Adapter Kit
