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Discussion Starter #1
I have a friend with a 2002 jetta 1.8t that won't start.
Throws a bunch of codes
P1850 data bus communication error
P0342 cam signal low voltage
P0172 a/f lean bank 1
He replaced the cam and crank sensors and no change.
Using a scope both sensors provide a clean pattern all the way back to the ecm harness.
It has spark and is triggering the injectors but not the fuel pump. I can remove the relay and jump the terminals to run the pump and get pressure. Still won't start. Removed timing cover and engine appears to be in time but never took the accessory belt off to verify it lines up exactly. Cranks normally and has compression. I don't know what else to check.
 

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Welcome, try posting in the MKIV forum. you will get more info there.

Possible Causes
Wiring from/to Camshaft Position Sensor (G40) faulty
Camshaft Position Sensor (G40) faulty
Timing misaligned

Possible Solutions
Check Wiring from/to Camshaft Position Sensor (G40)
Check Camshaft Position Sensor (G40)
Check Timing
 
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