The ECM also provides enhanced control of the engine for vehicle functions such as engine exhaust braking. The illustration on page 13 shows many of the OEM systems the ECM can monitor to provide enhanced vehicle performance, fuel economy and driver convenience.
The 3100 HEUI electronic system has some ability to diagnose itself. When a problem is detected, a diagnostic code is generated and the Check Engine/Service Engine Soon lamp is turned ON. In most cases, the code is also stored in permanent memory (Logged) in the ECM.
When diagnostic codes occur, they are called Active. They indicate a problem of some kind currently exists. They should always be serviced first. If a truck has an Active Code, find the code in the front of this manual and proceed to the indicated page to diagnose the cause.
Diagnostic codes stored in memory are Logged. Since the problem may have been temporary or may have been repaired since the time it was logged, logged codes do not necessarily mean something needs to be repaired. They are instead meant to be an indicator of probable causes for intermittent problems.
Some of the codes require passwords to clear. Codes not requiring passwords to clear are automatically deleted from memory after 50 ECM operating hours.
Diagnostic Codes Effect on Engine Performance
This manual contains a table listing all of the PID-FMI Diagnostic codes, along with the page number where details regarding the cause, performance affect, and troubleshooting of the code can be located.
The table on “PA-12: Possible Performance Effect of Active Diagnostic Codes” on page 46 lists all 3100 HEUI Diagnostic Codes, and whether each code may or may not affect engine performance.
The discussion on Engine Monitoring mentions the Check Engine Lamp flashes when a specific condition exists. When the ECM detects the engine problem, it generates an Active Diagnostic Code and also Logs the code to indicate when, and if appropriate, how many times the problem occurs. There are two types of Diagnostic Codes, Fault Codes and Event Codes.
Diagnostic Fault Codes are provided to indicate an electrical or electronic problem has been detected by the ECM. In some cases the engine performance can be affected when the condition causing the code exists. More frequently, however, the driver cannot detect any difference in the engine performance.
If the driver indicates a performance problem occurs whenever the Check Engine Lamp is flashing, one of the Diagnostic Codes may be the cause of the problem, and should be corrected.
If the driver does not indicate a problem with the engine performance and a Diagnostic Code is logged by the ECM, it indicates the ECM detected an abnormal condition, but it did not affect performance.
If this is the case, unless there are several occurrences of the specific diagnostic code in a very short period of time, or the ECM is indicating the problem exists at the present time, there is most likely nothing wrong with the electronic system.
Diagnostic Event Codes are provided to indicate operational problem has been detected in the engine (or truck) by the ECM. This usually does not indicate an electronic malfunction. Event codes typically are not an indication of an electronic system problem.
Lifetime Totals Stored In The ECM
The ECM maintains engine total data for the following parameters.
Engine Hours is engine running hours (it does not include time when the ECM is powered ON without the engine running).
Distance data requires a vehicle speed sensor connected to the ECM (the same sensor used for ECM vehicle speed).
PTO Hours and PTO Fuel are logged when engine rpm is set using the Cruise Control switches and the engine is operating under some load, or when the Dedicated PTO On/Off Switch is ON and vehicle speed is within range of the Idle/PTO Vehicle Speed Limit Parameter.
Idle Hours and Idle Fuel can include time when the engine speed is set using the Cruise switches and the vehicle speed is within range of the Idle/PTO Vehicle Speed Limit Parameter, but the engine is not operating under load.
Maintenance Indicator Data
The ECM records the Lifetime Data Totals when a maintenance reset occurs for three levels of maintenance – PM1, PM2, and Coolant Flush/Fill. The previous maintenance point is used by the ECM to calculate when the next maintenance is due.
The Maintenance Indicator feature is programmable to hours or distance. The PM1 maintenance is programmable to OFF, Automatic-Distance, Automatic-Hours, Manual-Distance, or Manual-Hours.
If PM1 is programmed to Automatic (Distance or Hours), the ECM calculates the next maintenance due by considering the vehicle operation history from the previous maintenance interval. If the vehicle has a history of poor fuel economy, the maintenance indicator will occur sooner than a vehicle with better fuel economy.
The ECM also uses the Engine Oil Capacity, with a larger capacity providing a longer maintenance interval. Engine Oil Capacity is programmed in quarts. If the PM1 Maintenance Indicator is programmed to Manual, the owner can program in their own specific maintenance mileage or time interval. PM2 and Coolant Flush/Fill intervals are determined by the factory.