Status Byte

Description and Operation 1-57

Powertrain Control Software

Bit 5

• 0 - The DTC test has not failed since last code clear

• 1 - The DTC test failed at least once since last code clear

Bit 4

• 0 - The DTC test completed since the last code clear

• 1 - The DTC test has not completed since the last code clear

Bit 3

• 0 - The DTC is not confirmed at the time of the request

• 1 - The DTC is confirmed at the time of the request

Bit 2

• 0 - The DTC test completed and was not failed on the current or previous monitoring cycle

• 1 - The DTC test failed on the current or previous monitoring cycle

Bit 1

• 0 - The DTC test has not failed on the current monitoring cycle

• 1 - The DTC test failed on the current monitoring cycle

Bit 0

• 0 - The DTC is not failed at the time of request

• 1 - The DTC is failed at the time of request

For DTCs that illuminate the MIL, a confirmed DTC means the PCM has stored a DTC and has illuminated the MIL. If the fault has corrected itself, the MIL may no longer be illuminated but the DTC still shows a confirmed status for 40 warm up cycles at which time the DTC is erased.

For DTCs that do not illuminate the MIL, a confirmed DTC means the PCM has stored a DTC. If the fault has corrected itself, the DTC still shows a confirmed status for 40 warm up cycles at which time the DTC is erased.

To determine if a test has completed and passed, such as after a repair, information can be combined from 2 bits as follows:

If bit 6 is 0 (the DTC test completed this monitoring cycle), and bit 1 is 0 (the DTC test has not failed on the current monitoring cycle), then the DTC has been evaluated at least once this drive cycle and was a pass.

If bit 6 is 0 (the DTC test completed this monitoring cycle) and bit 0 is 0 (the DTC test is not failed at the time of request), then the most recent test result for that DTC was a pass.

The status byte bits can be decoded as a 2 digit hexadecimal number, and displayed as the last 2 digits of the DTC, for example for DTC P0110:1C-AF, AF represents the status byte info.

Status Byte

A equals 1010 F equals 1111

Bit 7 equals 1 Bit 6 equals 0 Bit 5 equals 1 Bit 4 equals 0 Bit 3 equals 1 Bit 2 equals 1 Bit 1 equals 1 Bit 0 equals 1

Multiplexing

The increased number of modules on the vehicle necessitates a more efficient method of communication. Multiplexing is a method of sending 2 or more signals simultaneously over a single circuit. In an automotive application, multiplexing is used to allow 2 or more electronic modules to communicate simultaneously over a single media. Typically this media is a twisted pair of wires. The information or messages that can be communicated on these wires consists of commands, status or data. The advantage of using multiplexing is to reduce the weight of the vehicle by reducing the number of redundant components and electrical wiring.

2016 Powertrain Control/Emissions Diagnosis, Gasoline Engines, 3/2015