So my '99 cab had its first taste of LA stop and go traffic over the weekend. Unfortunately the heat seemed to get to it and the check engine light came on. I guess it leads a spoiled life here in SF. Luckily I had my trusty OBDII reader with me and read out a P1531. The next day the check engine light was still on. I then proceeded to drive 300 miles and then filled up the gas tank (with cheap gas btw) and then the check engine light went off.

I have been doing some searching for good threads on this but could use some help on what to do next. It seems that visually inspecting the cam sensor and actuator wiring to start makes sense.

BTW - speaking of HOT - LA girls are amazing.

 

Have you checked Imo's thread? https://rennlist.com/forums/996-foru...r-voltage.html

He had p1539 (bank2) and yours is bank1, similar code though. Not saying you have the exact problem but that shows it really takes quite a bit of exhaustive diagnostic to pinpoint the actual failure. Being intermittent will make diagnostic very difficult since even if the component passes the test, you cannot eliminate it. Maybe wait for the CEL to be ON more frequently?

Do you have Durametric?

 

Thanks Ahsai, I did find that thread. Unfortunately I don't have a Durametric. I guess I will start with the easy stuff (checking connections and cables) and go from there.

 

I just came across this thread...

http://www.renntech.org/forums/topic...on-with-p1524/

Scary stuff. $3000 for a Variocam job.

 

Yeah hence my suggestion of wait and see and preferably till it's more consistent so it's easier to diagnose (and harder to misdiagnose).

 

For months I've been chasing (with much help from others) misfiring problems and various related codes on my '02. In my experience the fault codes have been pretty much right on although we have gone on a number of scenic detours thinking we were smarter than the ECU. The ECU samples all its inputs over time and it knows when signals are correct and when they don't make sense.

It appears that the root causes of my problems have in fact been corroded ECU connections at the X59 connector pair in the engine compartment. Symptoms showed when the engine compartment gets hot. Even knowing this it is not easy to diagnose and repair because corrosion can reduce contact reliability even without visible signs.

IMHO the likely causes with an older car (10 years+) are going to be flaky connectors, sensor failures, or actuator failures. The ECU has its own connectors, through a wiring harness to the X59 connector, through the engine wiring harness to another connector, then finally into the sensor/actuator. Investigating each one of those for any wear or corrosion is worth the time.

 

Does anyone happen to know how the DME knows if the Variocam (via the solenoid) has successfully advanced the Cam or not (and throws a code) ? What sensors does it use to do this?

 

The cam position sensor, which also has its own error codes.

 

The crankshaft drives the exhaust cam (the lower one in the photo) via the double chain http://p-car.com/996/diy/engine/DSC_2901.JPG

The exhaust cam then drives the intake cam via a smaller chain whose tension is controlled by the variocam actuator. Diff tension creates diff timing between the two cams. The cam sensor picks up the cam position generated by the reluctor on the intake cam.

You can actually see the reluctor ring and the cam sensor clearly in this photo http://www.pelicanparts.com/techarti...mall/Pic07.jpg