Module Transmitted Invalid Data (Non SCP)

OBD II fault code U2011 is a generic trouble code that is defined as, “Module Transmitted Invalid Data (Non-SCP)”, and is set when the PCM (Powertrain Control Module) or any other capable control module detects incorrect data being transmitted between control modules over a serial communications system that does not follow the J1850 aka Standard Corporate Protocol (SCP) communications protocol.

Limited space precludes a comprehensive discussion on automotive communication protocols, but to keep things simple, we can explain the main differences between Standard Corporate Protocols and non-Standard Corporate Protocols- at least as far as the cheap generic code readers that most non-professional mechanics own are concerned.

It should be noted, however, that since the technical details of the two classes of communications protocols fall outside an article such as this, we will only provide a general overview of this topic.

Let us start with- Standard Corporate Protocol (SCP) “Standard Corporate Protocol” is the name carmaker Ford gave to a communications protocol that conformed to the J1850 standard, which is the standard all communications protocols have to follow to allow generic scan tools to communicate with a vehicle’s OBD II system.

In some ways, the acronym “SCP” became a kind of non-official standard for all communications protocols that were based on Ford’s interpretation of the J1850 standard, regardless of the vehicle that was using the protocol. The SCP protocol used a serial bus that was made up of two twisted wires that operated in the 0 to 5 volts range, and terminated on pins 2 and 10 in the standardized data link connector.

In practice, the SCP protocol was the most common communication link between the PCM and the transmission control module, but when the SCP protocol was largely replaced by Medium and High Speed CAN (Controller Area Network) communications systems by around 2006, many more (additional) vehicle control systems and modules operated on the SCP protocol.

Note that this protocol was not only the most common communications protocol on Ford products: it was also the most common protocol used in related makes, including Jaguar, Lincoln, Mercury, and others. Non-SCP protocols Briefly, non-Standard Corporate Protocols include (among others) the UART Based Protocol (UBP), FlexRay, as well as the various variants of the ubiquitous CAN (Controller Area Network) bus systems.

In practice, all modern vehicles use both Low Speed, Medium Speed, and High Speed Can bus systems as well as other systems and protocols in various combinations. For instance, a High Speed Can system will link control modules that monitor and control critical functions like the ABS and several Advanced Driver Assist Systems, while Medium Speed CAN bus systems will link control modules that monitor and control systems such as active suspension control, traction control, and stability control.

In practice, which control modules are linked by which communications system depends on equipment and systems fitted to the vehicle, but in all cases, High Speed CAN communications enjoy precedence over any other category of communications, thus preventing conflicts between various classes of control modules. As a practical matter, both Medium Speed and High Speed CAN systems use 2 wires for redundancy and both employ 0-1 volt signals using a 2.5-volt bias. Each protocol has “+” and “-” circuits.

Medium Speed CAN “+” and High Speed CAN “+”+ cycle from 2.5 to 3.5 volts, while Medium Speed SCAN “- “ and High Speed CAN “-“ cycle from 2.5 to 1.5 Volts. Moreover, vehicles that use a Medium Speed CAN system but it is not connected to the data link connector, those vehicles use specialized gateway modules that convert Medium Speed CAN communications to High Speed CAN communications.

In terms of operating principles, each control module on any given non-SCP communications system is programmed to both identify itself when it transmits data and to only recogni