so i cant get this P0336 code to go away after replacing the opti, but ive been reading that the pcm can be faulty if you have a P1661 code and the gauge cluster is ok. anyway, i unplugged the crank position sensor and started the car and it threw P0336 AND P1661, is that not an obvious sign that the computer is bad? i have another computer im about to copy my current tune into and see if this fixes it. also checked the voltage at the crank sensor connector, but im getting 12v, .050 v, .050 v. which doesnt seem 100% correct, im pretty sure i should be getting a 5v reference but not 100% sure. let me know what you guys think. its either chase my tail or spend $175 copying my tune onto another computer that i have.

 

What PCM ??? A ls1 will have 12v feed to The cam and crank sensors where as the e38 and alike will have 5v. As for the other problem I am unsure.

 

LT1 car

Heres some copy\paste:

DTC P0336 - CRANKSHAFT POSITION SENSOR CIRCUIT PERFORMANCE
NOTE:For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .
Circuit Description
CKP sensor is mounted in engine front cover and works in conjunction with 4X reluctor wheel on front of crankshaft. CKP sensor has battery power supply, ground and a signal circuit. As crankshaft rotates, reluctor wheel teeth interrupt a magnetic field produced by a magnet within sensor. Signals produced by sensor are monitored by PCM to accurately measure crankshaft velocity to detect misfire. This sensor is not used for spark control or fueling. For this diagnostic test, PCM monitors CKP sensor signal and low/high resolution signals from distributor.
DTC will set when following conditions are present:
 Engine speed 500-4000 RPM (LT1) or 675-4000 RPM (LT4).
 Ignition voltage 9-17 volts.
 CKP:LO RES ANGLE goes out of range from -10 DEV to +7 DEV but is still within -21 DEV to +51 DEV.
Diagnostic Procedures
1.Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING - 5.7L article. After performing OBD system check, go to next step. 2.If DTC P1371 or P1373 is also present, diagnose affected DTC first. If DTC(s) are not present, go to next step.
3.Start engine. Using scan tool, monitor CRANKSHAFT RPM. If RPM is indicated, go to next step. If RPM is not indicated, go to step 9).
4.Using scan tool, monitor CKP:LO RES ANGLE. Actual value may fluctuate, but should remain within range. If value is within range of -10 DEV to +7 DEV, go to step 7). If value is not within range, go to next step.
5.While observing CKP:LO RES ANGLE, quickly increase engine RPM once and allow to return to idle. If range changes from a positive value on acceleration to a negative value on deceleration, go to step 14). If value does not change, go to next step.
6.If value is fixed or outside of -10 DEV to +7 DEV range, go to step 15). If value is as specified, go to next step.
7.Using scan tool, select MISFIRE DATA LIST and monitor CYL MODE MISFIRE INDEX with engine at idle. Misfire index value should read 1000. If value is not as specified, go to next step. If value is as specified, go to step 12).
8.Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME and/or FAILURE RECORDS data and note parameters. Turn ignition off for about 15 seconds. Start engine and operate vehicle within conditions required for this diagnostic to run, and as close to conditions recorded in FREEZE FRAME/FAILURE RECORDS as possible. Select DTC function then enter DTC P0336. If scan tool indicates that this test failed this ignition, go to next step. If scan tool does not indicate that this test failed this ignition, see DIAGNOSTIC AIDS.
9.Turn ignition on, with engine off. Disconnect CKP sensor harness connector. Connect a test light between CKP sensor ignition feed circuit to battery ground at harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 17).
10.Connect test light between CKP sensor harness connector terminals "A" and "B". If test light illuminates, go to next step. If test light does not illuminate, go to step 18).
11.Install Signal Generator Tester (J 33431-B) to CKP sensor harness connector and ground. Turn ignition on. Turn tester on and set to generate a 54 MPH signal. Using scan tool, monitor crankshaft RPM. If scan tool indicates that crankshaft RPM is present, go to step 16). If crankshaft RPM is not indicated, go to step 13).
12.Visually inspect CKP sensor for physical damage, loose or improper installation, wiring routed too close to secondary ignition components or poor connections/terminal contact at sensor or PCM. Repair as necessary. After repairs, go step 22). If components or circuits are okay, go to step 20).
13.Turn ignition off. Disconnect PCM connector. Using DVOM, check continuity to signal circuit from sensor harness connector to PCM connector. If continuity is present, go to step 21). If continuity is not present, go to step 19).
14.Check excessive timing gear/chain wear. Repair as necessary. After repairs, go to step 22).
15.Check for poor connections/terminal at CKP sensor or for proper reluctor wheel installation. Repair as necessary. After repairs, go to step 22).
16.Check for poor connections/terminal tension at CKP sensor. Repair as necessary. After repairs, go to step 22). If connection or terminal tension is okay, go to step 20).
17.Repair ignition feed circuit. After repairs, go to step 22).
18.Repair ground circuit. After repairs, go to step 22).
19.Repair signal circuit. After repairs, go to step 22).
20.Replace CKP sensor. After replacing sensor, go to step 22).
21.Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
22.Using scan tool, select DTC, CLEAR INFO function. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter DTC P0336. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2).
23.Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.
Diagnostic Aids
Check for poor connections/terminal tension at CKP sensor. Check for excessive timing gear/chain tension, excessive distributor drive backlash, damaged crankshaft reluctor wheel or for improper installation. Check engine front cover assembly for damage or sensor coming in contact with reluctor wheel.
Using FREEZE FRAME and/or FAILURE RECORDS data mode may aid in locating an intermittent condition. If DTC cannot be duplicated, information included in FREEZE FRAME and/or FAILURE RECORDS data can be useful in determining how many miles since DTC set. FAIL COUNTER and PASS COUNTER can also be used to determine how many ignition cycles diagnostic reported a pass or a fail condition. To isolate when DTC failed, operate vehicle within same freeze frame conditions (RPM, load, vehicle speed, temperature, etc.).

 

Thanks sreve, this exactly what ive been looking for. ill see if i can get my hands on a scan tool for troubleshooting. much appreciated =).