In order to diagnose DaimlerChrysler vehicles equipped with an OBD II System, it is important that you understand the terms related to these test procedures. Some of these terms and their definitions are discussed in the next few articles.
The cylinder bank identifies the location of a specific component. For example, a specific group of engine cylinders may share a common control sensor and it would be identified as Bank 1, which is the location of cylinder No. 1 while Bank 2 identifies cylinders on the opposite cylinder head.
Data Link Connector
DaimlerChrysler vehicles equipped with OBD II Systems use a standardized Data Link Connector (DLC). It is typically located between the left end of the instrument panel and 12 inches past vehicle centerline. The connector is mounted out of sight from the passengers, but should be easy to see from outside by a technician in a kneeling position (door open).
The DLC is rectangular in design. It can accept up to 16 terminals. The DLC in the graphic to the right shows many common pin designations, but does not represent any specific vehicle.
OBD II DaimlerChrysler vehicle will have power at pin 16, and ground at pins 4 and 5. All other pins vary by year and model. All applications use the SCI circuits, but the pin assignments vary. All vehicles will utilize either the PCI bus, or the CCD bus circuits.
Both the DLC and Scan Tool have latching features that ensure that the Scan Tool will remain connected to the vehicle during operation.
Common uses of the Scan Tool while connected to the DLC include:
The term "pending code" is used to describe a fault that has been detected once and is stored in memory. This type of fault has not been detected on two consecutive trips (i.e., it has not matured into a hard code).
It is possible to access a "pending code" with a Generic Scan Tool (GST) on most DaimlerChrysler vehicles. Be aware that you may not be able to read a pending code with a Generic Scan Tool on some 1995 phase-in models.
If sensors are numbered (Bank 1 Sensor 1, or B1 S1), they follow the convention described above. If they are identified with letters ('A', 'B', 'C'), they are manufacturer defined. If only 1 sensor is used, the letter or number may be omitted.
If a "pending code" is set because of a Fuel System or Misfire Monitor detected fault, the vehicle must meet similar conditions for two consecutive trips before the code matures and the PCM activates the MIL and stores the code in memory. The meaning of similar conditions is important when you attempt to diagnose a fault detected by the Fuel System Monitor or Misfire Detection Monitor.
To achieve similar conditions, the vehicle must reach the following engine running conditions simultaneously (for the first failure recorded that set the code):
In many cases, an emission related system or component must fail a Monitor test more than once before it activates the MIL. The first time an OBD II Monitor detects a fault during a related trip, it sets a "pending code" in PCM memory. These codes appear when the Memory or Continuous codes are read. For a "pending code" to mature into a hard code (and illuminate the MIL), the original fault must occur for two consecutive trips (two-trip detection). However, a "pending code" can remain in the PCM for a long time before the conditions that caused the code to set reappear.Fuel Trim and Misfire Detection trouble codes can cause the PCM to flash the MIL after one trip because faults in these systems can cause damage to the catalytic converter.
A warmup cycle is defined as vehicle operation (after a cool-down period) when the engine temperature increases by at least 40ºF and reaches at least 160ºF.
Most trouble codes are cleared from the PCM memory after 40 "warmup cycles" if the fault does not reappear.