|Code||Fault Location||Probable Cause|
|P1340|| P1340 – CKP/CMP Sensor Signals Out Of Sequence (Audi, VW) |
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Manufacturer Specific Definitions for P1340
Table of Contents
- What Does Code P1340 Mean?
- Where is the P1340 sensor located?
- What are the common causes of code P1340?
- What are the symptoms of code P1340?
- Get Help with P1340
What Does Code P1340 Mean?
OBD II fault code P1340 is a manufacturer specific code that is defined by carmakers VW, Audi, Acura, and Volvo as “CKP/CMP Sensor Signals Out Of Sequence”, and is set on these applications when the PCM (Powertrain Control Module) detects that the output signals from the CKP/CMP are out of sequence.
NOTE: In this definition, the phrase “out of sequence” refers to the fact that the output signals from the Crankshaft Position Sensor (CKP) and Camshaft Position Sensor(s) (CMP) are out of phase with each other, or put differently, that the output signals from these sensors do not correlate with each other.
For a modern engine to operate efficiently, the PCM needs to “know” exactly where piston #1 is relative to the position of the camshafts at all times, since it is the position of piston #1 relative to the camshaft position(s) that largely determines the quality of the combustion process. While this position was relatively easy to measure on older engines, emission regulations are now such that the composition of the air fuel/mixture has to be controlled precisely on the one hand, and that combustion needs to be as complete as possible, on the other.
In order to satisfy these requirements, modern engines use crankshaft position sensors to monitor the position of piston #1 relative to a base setting, and camshaft position sensor(s) to monitor the position of the camshafts relative to the position of the crankshaft. Both positions are measured in degrees of crankshaft rotation, and in a fully functional engine, the positions of the crankshaft and camshafts will correlate with both each other, and a reference setting that is programmed into the PCM.
In practice, the position of the camshaft (typically the intake camshaft) is used by the engine management system to calculate appropriate fuel delivery strategies, while the position of the crankshaft (relative to a base setting), is used to calculate appropriate ignition timing strategies. Since both ignition and fuel delivery strategies have to be adapted continuously during normal engine operation to both minimize harmful exhaust emissions and to prevent premature or unstable combustion, the positions of the camshafts and crankshaft have to correlate exactly throughout the engine’s operating range for these adaptations to be effective without increasing emissions to unacceptable levels.
So when as a practical matter, the positions of the crankshaft and camshafts no longer correlate for whatever reason, it can happen that the ignition spark is delivered either too late or too early relative to fuel injection events, or, fuel injection events occur either to early or too late relative to the delivery of ignition sparks to individual cylinders. It is important to note however that the two conditions described above are not the same thing, and while both conditions might produce much the same symptoms, whichever condition obtains at any given moment depends on specific causes and therefore, the diagnostic and repair procedures for these conditions are different in meaningful ways.
Nonetheless, when the PCM detects that the positions of the crankshaft and camshafts do not correlate, or that (on some applications) the miscorrelation exceeds a maximum allowable threshold, it will recognize that it cannot control several vitally important engine and fuel management functions effectively, and it will set code P1340 and illuminate a warning light as a result.
Where is the P1340 sensor located?
The image above illustrates excessive slack in a timing chain on a VW engine, which is the main cause of code P1340 on VW VR6 engines in particular. In practice, there should be no observable slack in the timing chain between the timing chain sprockets on any engine: if there is slack present as there is in this example, the camshaft on the drive side of the timing system will rotate several degrees before the driven camshaft starts to rotate. When this happens, the correlation between the positions of the crankshaft and camshafts is lost, which results in the setting of code P1340 on VW, Audi, Acura, and Volvo applications.
What are the common causes of code P1340?
It should be noted that timing chain issues are extremely common on VR6 applications, and while issues with timing chains themselves are common, it should be noted that contrary to popular belief, timing chains to not “stretch”. What does happen is that the pins and bushings between links suffer excessive mechanical wear, thus creating excessive free play between every pin and bushing in the chain, which in turn, alters the overall length of the chain. In severe cases (as is common on VR6 applications) the excessive free play over the total length of the chain can eventually add up to more than the pitch (defined as the distance between pin centers) of a new chain.
Thus, given the fact that sprockets generally do not wear to the same extent that chain links do, the added length of a timing chain manifests as slack, which can produce significant miscorrelations between camshafts and crankshaft positions.
Nonetheless, other common causes of code P1340 could include one or more of the following-
- Low oil pressure, which could result in the timing chain tensioner being unable to maintain the correct chain tension
- Excessively worn chain guides, which could also result in the timing chain tensioner being unable to maintain the correct chain tension
- One or more excessively worn timing chain sprockets, but note that it is very unlikely that one sprocket would wear more than other sprockets on the same engine. Therefore, all sprockets must be replaced as a set
- Excessively worn timing belt on applications that use either timing belts alone, or on applications that use both timing belts and chains
- Defective camshaft position sensor(s)
- Defective crankshaft position sensor and/or sensor reluctor ring
- Use of incorrect, unsuitable, or substandard aftermarket sensors and/or reluctor rings
- Damaged, burnt, shorted, disconnected, and or corroded wiring and/or connectors in the crankshaft and/or camshaft sensors’ control/signal circuits
What are the symptoms of code P1340?
The most common symptoms of code P1340 are much the same across all applications, and could include one or more of the following-
- Stored trouble code and illuminated warning light
- One or more additional codes may be stored along with P1340, with misfire codes being the most common. Note that while it is not unheard of for no additional codes to be present, it is very unusual for no other codes to be present
- Engine may be hard to start, especially when the engine is cold
- In severe cases, the engine may not start although cranking speed may not be affected
- Idling may be rough or erratic, or the engine may stall at low speeds or when the affected vehicle comes to a stop
- In most cases, the engine may exhibit rough running or misfires at some engine speeds
- In almost all cases, fuel consumption will increase noticeably, which will almost always be accompanied by at least some loss of power. Note that power losses may occur only at some engine speeds, or throughout the engines’ operating range, depending on the nature and severity of the problem
- Mechanical noises such as rattling, scraping, or grinding sounds may be present which usually vary both in frequency and intensity with engine speed
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