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Old 12-08-2010, 11:11 PM
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bluebee bluebee is offline
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Location: San Jose, California
Join Date: Mar 2008
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Mein Auto: 02 BMW 525i M54 auto 130K
Originally Posted by TDS View Post
will a failing Camshaft Position Sensor throw a code ?
Notice this description from this excellent canonical thread about the CPS when it comes to failure modes ...

"M52TU engines (99-00) were the first with this vanos. They experience the cold weather cold start ideal jolt symptom, which is quite aggravating. This symptom was patched up in the M54 and M56 software.

So, M52TU cars have the most aggravated owners due to the cold morning symptom, but the M54 & M56 engine cars are also experiencing the vanos failure. They will experience a loss of torque and power, particularly in the lower RPM range (< 3K). They might also experience the lower RPM engine hesitations and hiccups.

As you know, owners are also now starting to experience engine fault codes. The fault codes are all related to the vanos exhaust side. The vanos exhaust side cylinder has a powerful spring inserted in it. The spring advances the piston by default to cause advanced exhaust valve timing. This assures no overlap in intake and exhaust valve opening at startup, allowing for a smooth startup. It takes significant oil pressure to oppose the spring and retard the piston. Due to failing (leaking) piston seals the DME becomes unable to retard the exhaust piston.

This scenario manifests in the following vanos exhaust side fault codes:
P1520 (BMW 104, 0x68): B (exhaust) Camshaft Position Actuator (faulty reference value).

P1523 (BMW 106, 0x6A): B (exhaust) Camshaft Position Actuator Tight or Jammed (mechanically stuck).

P1397 (BMW 18, 0x12): Camshaft Position Sensor B (exhaust) Circuit.
The Camshaft Position Sensor (CPS) is a common failure.

But if replacing the exhaust CPS (w/ OEM CPS) doesn't work then it's likely the vanos failure
. "

In addition, this is pertinent to misfires:"What are the symptoms of a failing vanos?
On autos with the M52TU engine (98/99-00) the failing vanos is causing engine idle jolts (dramatic drops) and possibly a stall on cold engine starts (< 55 F / 13 C).
On other cars with the M52TU, M54, M56 engines, car performance will be degraded. The engine will bog and hiccup at lower RPM's (< 3k). There will also be a general loss of torque and power, mostly at lower RPM's (< 3k).

How can I verify my vanos is failing?
On M52TU engine autos (98/99-00) experiencing the cold engine idle jolts, the vanos intake solenoid (metal cylinder) electrical connector can be disconnected. If the idle jolts cease then the problem is most likely the vanos."
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