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Programmable Parameters
Certain parameters that affect 3176 Diesel Truck Engine operation may be changed with electronic service tools (either the ECAP or DDT). The parameters are stored in the ECM, and are protected from unauthorized changes by passwords.These parameters are either "System Configuration Parameters" or "Customer Parameters". System Configuration Parameters are set at the factory and effect emissions or horsepower ratings within a family of engines. Factory passwords must be obtained and used to change System Configuration Parameters. Customer Parameters are variable and can be used to affect cruise control, vehicle speed limits, progressive shifting, rpm/horsepower ratings within the limits set by the factory, Caterpillar Engine Protection, and PTO operation. Customer Passwords are necessary to change Customer Specified Parameters.Some parameters may affect engine operation in ways a driver does not expect without adequate training. These may lead to power or performance complaints, even when the engine is performing to specifications.For example, the Vehicle Speed Limit (VSL) parameter is programmable, to allow the customer to electronically limit vehicle speed. When the programmed limit is reached, the ECM reduces the amount of fuel injected into the cylinders. Engine power is controlled and the VSL will not be exceeded. Also, Progressive Shift Parameters (such as Low Gear limits and High Gear limits) will cause the ECM to pause at a programmed engine rpm. This pause can be helpful to encourage more fuel efficient driving practices but may be misunderstood by the driver and result in a performance complaint.Passwords
"System Configuration Parameters" are protected by factory passwords. Factory passwords are calculated on a computer system available only to Caterpillar dealers. Since factory passwords contain alphabetic characters, only the ECAP may change System Configuration Parameters. System Configuration Parameters affect horsepower family or emissions."Customer Parameters" are protected by customer passwords. The customer passwords are programmed by the customer. Either the ECAP or DDT may change customer Parameters (although if a customer programs his password with alphabetic characters using an ECAP, only an ECAP can change Customer Parameters, since the DDT does not have alphabetic characters). See section 2.0 on "Programming 3176 Parameters", for more details when passwords are needed and how to obtain them.Self-Diagnostics
The 3176 electronics have some ability to diagnose themselves. When a problem is detected, a diagnostic code is generated and the diagnostic lamp is turned on. In most cases, the code is also stored in permanent memory in the ECM.Codes that represent current faults are called ACTIVE. They indicate that a problem of some kind currently exists. They should always be serviced first. See the section on "Troubleshooting Diagnostic Codes" in this manual for more details.Codes stored in memory are called LOGGED. Since the problem may have been temporary or may have been repaired since the time it was logged, logged codes don't necessarily mean something needs to be repaired. They are instead meant to be an indicator of probable causes for intermittent problems. In addition, some logged codes record "events", rather than failures. Codes not requiring passwords to clear are automatically deleted