P1955 – Glow Plug Control Module 2 to PCM Comm. Circuit Range/Performance (Mercedes, Sprinter)

By Reinier (Contact Me)
Last Updated 2019-03-27
Automobile Repair Shop Owner

Table of Contents

1. What Does Code P1955 Mean?
2. Get Help with P1955

What Does Code P1955 Mean?

On the face of it, and according to some generic diagnostic equipment, code P1955 is a manufacturer specific code that is defined by carmaker Mercedes, and sometimes by Chrysler, as “Glow Plug Control Module 2 to PCM Comm. Circuit Range/Performance”. Also according to some generic diagnostic equipment, this code is set particularly on Sprinter vans when the PCM (Powertrain Control Module) detects an abnormal voltage in the communication circuits between the PCM and the glow plug control module.

However, it should be noted that-

• Neither Mercedes, nor Chrysler official sources list code P1955 as a code that is specific to any Mercedes or Chrysler application. In fact, code P1955 does not appear in technical Mercedes and/or Chrysler sources at all
• While there are manufacturer specific codes that have the letter “9” as a third character, the letter “9” refers to the transmission. Thus, in this case, the letter “9” would refer to the transmission as a system, while the “55” would describe a specific issue within the transmission, and not to the glow plugs or the glow plug control module in way

NOTE: As a practical matter, the definition “Glow Plug Control Module 2 to PCM Comm. Circuit Range/Performance” is assigned to code P0684, which is a generic code that applies to all applications that are fitted with glow plugs and glow plug control modules.

Nonetheless, many users of both cheap generic code readers and apps that work through smart phones, also report that their equipment finds code P1955 on Sprinter vans with gasoline engines. In some of these cases, the code refers to issues with the throttle body, which on some Sprinter variants can cause a fail-safe or limp mode if the problem is not resolved.

It is not exactly clear how code P1955 came into existence, nor how it came to be listed in some resources as being related to the glow plug control module on Sprinter vans. What is known however, is that most cheap generic coder readers that are made in the Far East, as well as many smart phone apps run on pirated diagnostic software that is widely, and freely  available on the internet. It is therefore likely that a corrupted copy, or more likely, a sabotaged copy of such pirated software had made into the products of one Chinese manufacturer, and from there, it had spread to other manufacturers and producers of smart phone apps.

It should be noted though that although some very well equipped independent repair shops might have access to dealer-grade diagnostic equipment, some aspects of this class of diagnostic software, such as proprietary PID (Fault Parameter Identifier) information is never released to the independent repair trade in general, and to the manufacturers of aftermarket diagnostic equipment, in particular.

Therefore, the only way to prevent such misdiagnoses on Mercedes and Chrysler products, and particularly on Sprinter vans, is to have the vehicle scanned with Mercedes’ proprietary Star Diagnosis System, or with Chrysler’s proprietary WiTECH diagnostic software at a dealership.

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