Te dejo la lista de códigos de fallo del c18xe:

Código:
Siemens Simtec 56.0/56.1


Fault:
12 	Initiation of diagnosis. 	n/a
13 	Oxygen sensor 	Open circuit
14 	Coolant temperature sensor 	Voltage low
15 	Coolant temperature sensor 	Voltage high
16 	Knock sensor signal circuit 	No change in voltage
19 	Incorrect Revs per Minute (RPM) signal (crankshaft sensor) 	Incorrect signal, check sensor
21 	Throttle position sensor (TPS) 	Voltage high
22 	Throttle position sensor (TPS) 	Voltage low
23 	Knock control module signal 	Out of range
24 	Vehicle speed signal (VSS) 	No signal
25 	Injector valve 1 	Voltage high
26 	Injector valve 2 	Voltage high
27 	Injector valve 3 	Voltage high
28 	Injector valve 4 	Voltage high
37 	Check light (fault code lamp) 	Voltage low
38 	Oxygen sensor circuit 	Voltage high
39 	Oxygen sensor circuit 	Voltage low
44 	Oxygen sensor 	Lean exhaust (weak mixture)
45 	Oxygen sensor 	Rich exhaust (rich mixture)
48 	Battery 	Voltage low
49 	Battery 	Voltage high
52 	Check light (fault code lamp) 	Voltage high
53 	Fuel pump relay 	Voltage low
54 	Fuel pump relay 	Voltage high
55 	Engine Control Unit (ECU) faulty 	Check chassis earth and ECU connector.
56 	Idle air control 	Voltage high
57 	Idle air control 	Voltage low
61 	Fuel tank vent valve 	Voltage low
62 	Fuel tank vent valve 	Voltage high
69 	Intake air temperature sensor 	Voltage low
71 	Intake air temperature sensor 	Voltage high
73 	Mass air flow temperature 	Voltage low
74 	Mass air flow temperature 	Voltage high
75 	Torque control (automatic) 	Voltage low
76 	Torque control (automatic) 	Continuous signal, ignition retard long
81 	Injector valve 1 	Voltage low. Injector short circuit to ground.
82 	Injector valve 2 	Voltage low. Injector short circuit to ground.
83 	Injector valve 3 	Voltage low. Injector short circuit to ground.
84 	Injector valve 4 	Voltage low. Injector short circuit to ground.
87 	Air Conditioning (A/C) cut-off relay 	Voltage low
88 	Air Conditioning (A/C) cut-off relay 	Voltage high
91 	Oxygen sensor heater 	Voltage high
92 	Camshaft sensor 	Incorrect signal
98 	Oxygen sensor heater 	Voltage low, open circuit
La cosa sería ver si después de cambiar el sensor del árbol de levas seguía marcando el fallo. Mira también si tiene algún otro fallo guardado.