P1999 – Mfg Defined (Mercedes-Benz, Volvo, Volkswagen)


By Reinier (Contact Me)
Last Updated 2016-08-04
Automobile Repair Shop Owner

Trouble CodeFault LocationProbable Cause
P1999 Load limit is active (Mercedes-Benz) Cylinder deactivation malfunction (Volvo S-series) Engine management issues (Volvo XC-series) Friction too High, Exhaust Cam Adjustment Bank 2 (VW VAG-COM)

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What Does Code P1999 Mean?

PLEASE NOTE: The information in this article is for general informational purposes only, and is therefore not definitive, nor exhaustive. As such, this information must NOT be used in any diagnostic and/or repair procedure that involves OBD II fault code P1999. Always refer to the relevant repair manual, or refer the vehicle for professional diagnosis and repair.

OBD II fault code P1999 falls into series of manufacturer-specific codes that is “reserved” for transmission relates issues, but to date, very few major car makers have assigned P19XX-series codes to specific transmission related issues, with Ford being foremost.

P1999 is not in widespread use and only a few car makers use it at all. Below are some details of which car makers use code P1999, and what this code means for these manufacturers. Note that in most cases, extracting code P1999 requires professional grade diagnostic equipment as well as product-specific knowledge to correctly interpret the significance of this code as it pertains to the particular vehicle or application that displays the code.

Mercedes-Benz and P1999

P1999 definition: “Load limit is active.”

Load limiting refers to measures taken by a PCM to limit the loads placed on the drive train under certain driving conditions and throttle positions. Note that on some diagnostic equipment, this code can also be displayed as – P20D4 – but with the same definition.

Code P1999 explained:

Code P1999 is used on some high performance MB models to indicate that there is a problem with PCM programming that protects drive train components against high torque outputs that could potentially damage those components.

Essentially, the PCM on these models are programmed to detect when engine power output exceeds predefined levels; when this level is reached, power output is reduced momentarily to protect the transmission and other drive train components. One way of achieving this reduction in power is for the PCM to close the throttle plate, and to make adjustments to fuel delivery and ignition timing to limit engine power.

However, suddenly closing the throttle plate has the effect of causing a severe stumble that some drivers describe as “…driving into a brick wall.” This effect typically occurs when the throttle is opened suddenly, and it can occur at any throttle position between about 25%, and 75% open, but only when the rate at which the throttle is opened exceeds a predefined value. Gradually opening the throttle, or cruising at large throttle openings will typically not activate the load limiting feature.

Code P1999 is set when the load limiting circuits remain active, producing symptoms that can vary from poor acceleration, stalling upon acceleration; rough running/idling, decreased fuel economy, and others that may be specific to the affected vehicle.

Fixing code P1999:

Reprogramming MB PCM’s to repair or remove load limiting circuits is a highly technical fair that requires specialized equipment, and expert knowledge of MB diagnostics and programming. Therefore, this procedure should NOT be attempted by non-professional mechanics.

NOTE: On some MB applications that use MAF (Mass Airflow) sensors, instead of the more common MAP (Manifold Absolute Pressure) sensors, such as some M-class vehicles, a faulty or non-OEM MAF sensor can trigger code P1999. In these cases, the code can often be resolved simply by cleaning or replacing the MAF sensor.

Volvo S-series models and P1999

P1999 definition: “Cylinder deactivation malfunction”.

Note that in some definitions the wording may be slightly different, but in Volvo S-series applications, including the S40, S60, S70, S80, S90, and SCC, models, this code refers to cylinder deactivation issues.

Code P1999 explained:

Cylinder deactivation refers specifically to the practice of deactivating some cylinders on an engine to reduce emissions. In Volvo applications, the deactivation is accomplished by interrupting the flow of pressurized oil to hydraulic valve lifters, thereby preventing the valves on some cylinders from opening and closing, which has the result of inactivating selected cylinders.

Fixing code P1999:

Although diagnostic and repair procedures are for the most part model specific, the causes if this code on Volvo applications can almost always be traced to poor maintenance, and/or the use of inappropriate engine lubricating oil that affects the operation of control solenoids and valves.

Volvo XC-series models and P1999

P1999 definition: Although there is no defined description for this code on XC-series models, the presence of this code indicates engine management issues.

Fixing code P1999:

Diagnostic and repair procedures are dependent on the actual problem, which can only be determined by using suitable diagnostic equipment to extract the code (and its definition) from the fault memory.

VAG-COM Diagnostic System and P1999

VAG-COM Diagnostic System” refers to a Microsoft Windows-based diagnostic system used primarily by Volkswagen Group vehicles, including SEAT, Audi, and Skoda models, along with many VW commercial vehicles. “VAG-COM” is derived from Volkswagen AG, which was the former name of the Volkswagen Group.

P1999 definition: “Friction too High, Exhaust Cam Adjustment (Bank 2)”. “Friction” refers to friction in the mechanism that alters the valve timing on the exhaust camshaft of the bank of cylinders that does not contain cylinder #1.

Typical symptoms could include an illuminated warning light, rough running/idling, hard starting, loss of power, and increased fuel consumption. In some cases, the vehicle could enter limp mode.

Fixing code P1999:

In almost all cases, the cause can be traced to poor maintenance, and/or the use of unsuitable engine lubricating oil that does not provide sufficient lubrication. The presence of solid particulate matter in the oil, such a sludge or metal wear particles can also cause this code.

Other Manufacturer Specific Definitions for P1999

Friction Too High Exhaust Camshaft Adjustment Bank 2 (Volkswagen)
Friction Too High Exhaust Camshaft Adjustment Bank 2 (Audi)

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