|Code||Fault Location||Probable Cause|
|P1338|| P1338 – Camshaft Position Sensor Bank 1 Open Circuit Or Short To Positive (Audi, VW) |
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Manufacturer Specific Definitions for P1338
|Audi||Camshaft position (CMP) sensor, Bank 1 - open circuit/short to positive|
|Daewoo||#8 Misfire Circuit - Open|
|Hyundai||#8 MF Signal Line Short|
|Peugeot||Cylinder No.2 misfires|
|Volkswagen||Camshaft position (CMP) sensor, open circuit/short to positive|
What Does Code P1338 Mean?
OBD II fault code P1338 is a manufacturer-specific trouble code that is defined on VAG-group (VW, Audi, etc.) vehicles as “Camshaft Position Sensor Bank 1 Open Circuit or Short to Positive”, and is set when the PCM (Powertrain Control Module) detects either an open circuit or a short circuit in the circuits that are associated with the camshaft position sensor on Bank 1. Note that the camshaft referred to in this code is typically the intake camshaft on “Bank 1”, which refers to the bank of cylinders on V-type engines that contains cylinder #1.
Most modern engine management systems use dedicated position sensors on one or more camshafts to determine the position of cylinder #1 relative to both a fixed reference point and the phasing of the camshaft relative to the position of the crankshaft. This information is required to determine appropriate ignition and fuel injection strategies for cylinder #1 to allow the engine to start.
In theory, it is possible to supply an ignition spark and fuel to any cylinder that is at the top of its compression stroke to start an engine, but doing this will require an overly complicated monitoring system that will have to monitor the position of every piston. Therefore, all modern engines use a simplified system that monitors only the position of cylinder #1, on the assumption that if cylinder #1 starts successfully, all the other cylinders will also start, since it follows that if cylinder #1 is phased correctly relative to the crankshaft, the other cylinders will also be phased correctly.
As a practical matter, engines cannot monitor the position of piston #1 directly. This position is inferred based on a fixed reference point that the crankshaft position sensor detects, and assuming that there are no issues with the timing belt or timing chains(s) and related components, by a fixed reference point on one or more camshafts that are detected by camshaft position sensors.
If the position of the camshaft correlates with the position of the crankshaft, the PCM will “know” when piston #1 is at, or close to the top of its compression stroke, and it uses this information to deliver both an ignition spark and fuel to cylinder #1 at the appropriate moment to start the engine.
Therefore, if the PCM does not receive valid information about the position of cylinder #1 because of a shorted or open circuit in the camshaft position sensor’s circuits, it cannot infer the position of cylinder #1 accurately, if at all. If this happens, the PCM will recognize that it cannot control, monitor, or manage neither the fuel delivery, nor the delivery of an ignition spark to cylinder #1 effectively, and it will set code P1338 and illuminate a warning light as a result.
Where is the P1338 sensor located?
This image shows the area (circled in green) where camshaft position sensors are typically located on some V-type Audi engines. However, some Audi engines have undergone many iterations in the past 15 years or so, which means that even professional mechanics sometimes have trouble locating some sensors. Therefore, it is recommended that relevant and up-to-date service information be consulted to locate and identify the camshaft position sensor correctly to avoid confusion and the likely unnecessary replacement of the wrong parts.
What are the common causes of code P1338?
Typical causes of code P1338 on VAG-group vehicles are largely similar across all applications, and could include one or more of the following-
- Damaged, burnt, shorted, disconnected, or corroded wiring and/or connectors in the camshaft position sensor’s control or signal circuits
- Damaged, burnt, shorted, disconnected, or corroded wiring and/or connectors in a reference voltage circuit in cases where the camshaft position sensor shares a reference voltage circuit with other engine sensors
- Damaged, defective, or malfunctioning camshaft position sensor
- An incorrectly installed camshaft position sensor
- Use of a substandard aftermarket camshaft position sensor
- Failed or failing PCM, but that since this is a rare event, the fault must be sought elsewhere before any control module is replaced or reprogrammed
What are the symptoms of code P1338?
Common symptoms of code P1338 on VAG-group vehicles are similar across all applications, and could include one or more of the following-
- Stored trouble code and illuminated MIL (CHECK ENGINE) light
- Multiple codes, including codes relating to other, unrelated engine sensors could be present if the problem involves reference voltage circuits
- A no-start condition will almost certainly be present, although the engine may crank normally
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