ABS PHT?

georg · April 1, 2016

What does PHT stand for?

With the Tech2, you are asked to select between ABS and ABS PHT. Also, in the GM service manual, the description for code C0570 is "ECU performance PHT"

georg · April 3, 2016

Thanks, that solves the mystery.

GM also mentions ECE 13 in its service manual without defining it. This is in reference to the ABS light staying on after some codes are cleared till the next time the truck reaches at least 13 km/hr

Googling produced the answer. United Nations Economic Commission for Europe, Regulation 13 (covers braking system).

Apparently the 13 is unrelated to the 13km/hr.

georg · April 1, 2016

Googling ABS PHT does not bring up any results.

cjb321 · April 2, 2016

Found this buried in a post on another truck forum through google search, just copied and pasted it. Not sure if it will help but it was all i could find lol:

Data Link Communications Description and Operation
Circuit Description
The serial data communication among the control modules is performed through multiple serial data communication links. The class 2 serial data line is always present. The high speed GMLAN or controller area network (CAN) may be present for different vehicle options. The data link connector (DLC) allows a scan tool to communicate with the modules on class 2 or high speed GMLAN serial data lines. In order for the scan tool to communicate with the modules on high speed GMLAN link, a CANdi module is needed. The CANdi module behaves as an interface between the scan tool and the high speed GMLAN data link. The CAN is used for functional communication only, among the modules connected to it.

Data Link Connector (DLC)
The data link connector (DLC) is a standardized 16 cavity connector. Connector design and location is dictated by an industry wide standard, and is required to provide the following:

Scan tool power battery positive voltage at terminal 16
Scan tool power ground at terminal 4
Common signal ground at terminal 5
Class 2 signal at terminal 2
High speed GMLAN serial data bus (+) at terminal 6
High speed GMLAN serial data bus (-) at terminal 14
Class 2 Serial Data Line
Class 2 serial data is transmitted on a single wire at an average of 10.4 kbps. This value is an average, class 2 uses a variable pulse width modulation to carry data and depending on the message it may operate faster or slower. The bus will float at a nominal 7 volts during normal operation. Each module can pull this lower during the transmission. The bus is not at battery positive voltage or ground potential during normal operation. When the ignition switch is in RUN, each module communicating on the class 2 serial data line sends a state of health (SOH) message every 2 seconds to ensure that the module is operating properly. When a module stops communicating on the class 2 serial data line, for example if the module loses power or ground, the SOH message it normally sends on the data line every 2 seconds disappears. Other modules on the class 2 serial data line, which expect to receive that SOH message, detect its absence; those modules in turn set an internal DTC associated with the loss of SOH of the non-communicating module. The DTC is unique to the module which is not communicating, for example, when the inflatable restraint sensing and diagnostic module (SDM) SOH message disappears, several modules set DTC U1088. Note that a loss of serial data DTC does not normally represent a failure of the module that set it.

The class 2 serial data line on this vehicle is a star configuration. The powertrain control module (PCM) has an additional class 2 serial data circuit to body control module (BCM). If one of the class 2 serial data circuits to the PCM opens, communication will not be interrupted. The following modules communicate on the class 2 serial data line:

The audio amplifier (AMP), w/UQ7 and Y91
The body control module (BCM)
The communication interface module (OnStar®), w/UE1
The digital radio receiver (DRR), w/U2K
The driver door module (DDM)
The electronic brake control module (EBCM)
The generator battery control module (GBCM)
The HVAC control module
The hybrid control module (HCM), w/HP2
The inflatable restraint sensing and diagnostic module (SDM)
The instrument panel cluster (IPC)
The memory seat module (MSM), w/AN3
The passenger door module (PDM)
The powertrain/engine control module (PCM/ECM)
The radio
The rear seat audio (RSA) controller, w/UK6
The rear seat entertainment (RSE) assembly w/U42
The rear wheel steering control module (RWSCM), w/NYS
The remote playback device - CD player (CDX), w/U1S
The transfer case shift control module (TCSCM), w/NP1/NP8
The transmission control module (TCM), w/M74
The class 2 serial data line allows a scan tool to communicate with these modules for testing purposes, checking for DTCs, and to activate/enable/disable functions. These class 2 serial data circuits are bussed together via 2 splice packs:

SP205--Located behind the instrument panel (I/P) near the headlamp switch connector.
SP207--Located in the I/P harness.
Refer to Computer/Integrating Systems Component Views .

Controller Area Network (CAN) Serial Data Line w/6.6L Engine
The controller area network (CAN) serial data line does not communicate with the scan tool via the data link connector (DLC). CAN serial data information is interpreted by the modules that are on the class 2 also, and transmitted to the scan tool. The following modules communicate on the CAN serial data line:

The engine control module (ECM)
The transmission control module (TCM)
The fuel injection control module (FICM)
The glow plug control module (GPCM)
The CAN serial data line, based on J1939 SAE standard, is high speed serial data bus used to communicate information among the modules. Typical data-transmission speeds must be high enough to ensure that the required real-time response is maintained.

The addressing scheme employed with CAN assigns a label to every message, with each message receiving a unique identifier. The identifier classifies the content of the message. Each module processes only those messages whose identifiers are stored in the module's acceptance list. This is CAN's form of message filtering.

The identifier labels both the data content and the priority of the message being sent. Each module can begin transmitting its most important data as soon as the bus is unoccupied. When more than one module starts to transmit simultaneously, the message with the highest priority is assigned first access. A module responds to failure to gain access by automatically switching to receive mode, the module then repeats the transmission attempt as soon as the bus is free again.

High Speed GMLAN Serial Data Line (PHT)
The data link connector (DLC) allows a scan tool to communicate with the high speed GMLAN serial data circuit through the CANdi module. The serial data is transmitted on two twisted wires that allow speed up to 500 Kbps. The twisted pair is terminated with two 120-ohm resistors, one is internal to the engine control module (ECM) and the other is internal to the energy storage control module (ESCM). The resistors are used to reduce noise on the high speed GMLAN bus during normal vehicle operation. The high speed GMLAN is a differential bus. The high speed GMLAN serial data bus (+) and high speed GMLAN serial data (-) are driven to opposite extremes from a rest or idle level. The idle level which is approximately 2.5 volts is considered a recessive transmitted data and is interpreted as a logic 1. Driving the lines to their extremes adds 1 volt to high speed GMLAN serial data bus (+) and subtracts 1 volt from high speed GMLAN serial data bus (-) wire. This dominant state is interpreted as a logic 0. GMLAN network management supports selective start up and is based on virtual networks. A virtual network is a collection of signals started in response to a vehicle event. The starting of a virtual network signifies that a particular aspect of the vehicles's functionality has been requested. A virtual network is supported by virtual devices which represents a collection of signals owned by a single physical device. So, any physical device can have one or more virtual devices. The signal supervision is the process of determining whether an expected signal is being received or not. Failsofting is the ability to substitute a signal with a default value or a default algorithm, in the absence of a valid signal. Some messages are also interpreted as a "heartbeat" of a virtual device. If such a signal is lost, the application will set a no communication code against the respective virtual device. This code is mapped as a code against the physical device. Note that a loss of serial data DTC does not normally represent a failure of the module that set it.

The powertrain control module (PCM) and hybrid control module (HCM) are functionally communicating on both class 2 and high speed GMLAN data links. However the diagnostic communication of the above modules with the scan tool is performed on class 2 data link only. All DTCs set by the high speed GMLAN modules, including HCM, are reported by the PCM on class 2. Data displaying, output controls and programming of the control modules connected to high speed GMLAN only, is performed through high speed GMLAN link.

The GMLAN serial data communications circuit is in a linear topology. The following modules are connected to the link, in order from DLC to the end of the linear configuration:

The energy storage control module (ESCM)
The starter/generator control module (SGCM)
The electro-hydraulic power steering (EHPS)
The hybrid control module (HCM)
The powertrain control module (PCM)