VT CEL/Diagnostic without BCM?

[Drew_au]

I posted these questions some time ago in another thread - maybe they should have been posted here.

Yoda69 has kindly re-written my VT V8 chip to remove the security link - but I'm wondering about diagnostics - any recommendations?

The main concern I have is regarding the Check Powertrain Light. I plan to run the VT engine just with the PCM (and it appears this is possible thanks to Yoda69's work) but how will I ever know if the system is "throwing a code". From what I can glean from the factory manual there is no diagnostic LED output from the PCM other than a serial data link and a diagnostic mode input pin. Is a scanner or computer link the only way?

Once again - my apologies for my lack of know how - 95% of it makes sense - it's just a matter of getting the final details together.

Thanks,

Andrew.

[The1]

the codes will spit out with the ecu codes if there is any.

EDIT: BCM is Body Control Module, nothing to do with trans.

[The1]

here's the fault codes for vt

Fault Codes
12 Satisfactory operation
13 RH Oxygen sensor (no signal)
14 Coolant temperature sensor (voltage low)
15 Coolant temperature sensor (voltage high)
16 Coolant temperature sensor (voltage unstable)
17 ECU failure (coolant sensor circuit)
18 EGR flow fault
19 Throttle position sensor (sticking open)
21 Throttle position sensor (voltage high)
22 Throttle position sensor (voltage low)
23 Air temperature sensor (voltage high)
24 Vehicle speed sensor (no signal)
25 Air temperature sensor (voltage low)
26 Air temperature sensor (voltage unstable)
29 EGR position sensor fault
31 Theft deterrent signal missing
32 Air flow sensor (voltage out of range)
35 Idle speed error (IAC valve unable to control idle speed)
36 Vacuum leak
41 Electronic spark timing (EST) circuit
42 Electronic spark timing (EST) bypass circuit
43 Knock sensors
44 RH oxygen sensor (lean signal)
45 RH oxygen sensor (rich signal)
46 Crank angle reference signal (engine will not start)
47 Crank angle reference signal (no signal)
48 Cam angle sensor (no signal)
49 Cam angle or crank angle sensor (signal intermittent)
51 Mem-Cal error
54 ECU power supply circuit (voltage variation, terminal A4)
55 Faulty ECU
56 Lean condition under load (supercharged engine)
57 Injector power supply monitor (voltage variation, terminal B12)
63 LH oxygen sensor (no signal)
64 LH oxygen sensor (lean signal)
65 LH oxygen sensor (rich signal)
66 3-2 Shift Control Solenoid Circuit Fault
67 Torque Converter Clutch On-Off Solenoid Control Circuit
69 Torque Converter Clutch Stuck On
72 Vehicle Speed Sensor Intermittent While Driving
73 Pressure Control Solenoid Current
75 System Voltage Low
76 Air/Fuel ratio (variation between left and right banks)
78 Air/Fuel ratio (variation between left and right banks)
91 Quad driver surface module fault
92 Low speed fan fault
93 Knock sensors
94 Vehicle speed sensor, M/T (no signal)
95 Traction control signal (out of range)
96 A/C pressure sensor fault
97 Canister purge solenoid

[The1]

here's the VT V8 PCM wiring diagram
https://pcmhacking.net/forums/view ... f=32&t=794

Pin A4?? maybe check that.

[Drew_au]

Thanks for the reply.

From what I understand the Check Engine Light and the diagnostic connector come from the BCM - not the PCM - hence my question. OR do I have the wrong handle on it, can the codes be extracted straight from the VT PCM (that would be great if it was the case)?

Here's the schematic that makes be believe the CEL is run by the BCM:

VTV8Diagnostic.jpg

If the PCM can spit out codes, are they accessed by earthing YB128-6 and using a test LED on YB128-9?

Andrew.

[Drew_au]

If the PCM can spit out codes, are they accessed by earthing YB128-6 and using a test LED on YB128-9?

Just had a closer look, pin 9 is the serial data so I doubt it would run the codes to a test lamp.

Andrew.

[Drew_au]

here's the VT V8 PCM wiring diagram
https://pcmhacking.net/forums/view ... f=32&t=794

Pin A4?? maybe check that.

Pin A4 is B+, also goes to CEL. Then the -ve side of the CEL is switched by the BCM. (Back to my original problem, I'm not running the BCM.

I'm sure someone must have been through this before fitting a VT V8 to another vehicle and deleting the BCM, unless everyone has just downgraded to a earlier ECU (I don't want to do that though).

Still searching various forums,

Andrew.

[The1]

yeh ok, sorry i havn't had experience with VT, but even so the codes should still be logged in the PCM so you could use a laptop or scantool to pull the codes.

[Drew_au]

yeh ok, sorry i havn't had experience with VT, but even so the codes should still be logged in the PCM so you could use a laptop or scantool to pull the codes.

Yeah, I'm starting to think that's the only way - forget flashing the codes or having a CEL - just use a serial link to the laptop.

Now to learn about using the laptop! Any guides I should read as a newbie?

Thanks again,

Andrew.

[charlay86]

How about having a BCM with only the necessary connections power/ground/data etc. and a CEL?