Hilton

iTrader: (36)

The most recent theory is that the PCM or perhaps the BCM (new one for me) has a problem.

https://ls1tech.com/forums/general-m...strated-2.html

With the starter relay manually grounded, I can drive the car.

Thanks in advance guys.

01ssreda4

iTrader: (96)

OK, so the status is: all relays/fuses are functioning perfect after being checked and rechecked. Fusible links appear to be in perfect shape. Everything functions, including the motor running, except the gauges (the Voltage gauge does work). So no tach, speedo, oil, temp, or fuel level. And it had a no start condition. I verified at the starter relay's location that it did in fact have a 12+ key signal, a 12+hot, and using a jumper verified that the path to the starter was in fact good. It didnt however have a ground. I believe this wire was yellow with a black stripe. I gave this wire a ground and plugged the relay back in and the start functions normally but still no gauges.

01ssreda4

iTrader: (96)

O and another important detail I left out. The OBD scanner will not log in and scan the car. It just says waiting for vehicle to respond and can never communicate with the car's computer.

flame

iTrader: (13)

The starter relay is controlled by the BCM and the gauges get there signal through the serial data line from the PCM. Kinda hard to fix over the net. You need to get some wiring diagrams and start testing inputs/outputs to locate the problem.

01ssreda4

iTrader: (96)

Could we get another bcm and swap it in? Or will the VINs have to match or whatever?

Hilton

iTrader: (36)

And a Christmas bump!

01ssreda4

iTrader: (96)

put your egg nog down and help us figure this out

eallanboggs

iTrader: (1)

Have you checked the power and grounds at the DLC connector to make sure you don't have a short to power or ground? This would pull your network down.

Hilton

iTrader: (36)

No I haven't. I'll look to see what DLC stands for and check it out.

WhiteBird00

iTrader: (4)

Yes, the yellow/black wire is the ground for the starter relay coil (control) circuit but it doesn't just go to chassis ground. It is grounded through the BCM as part of the VATS system. If the BCM doesn't detect the correct resistance in the ignition key pellet, it disables the starter by preventing ground on the relay and it disables the fuel system by not providing a "fuel enable" signal to the PCM.

Did you test the lighter/accessory fuse during your testing? That is the fuse that protects the OBD connector.

No, you can't swap another used BCM and expect it to work unless you bypass the VATS. A new BCM programs itself to the key pellet the first time it's used and can't be reprogrammed after that. So you would have only a 1 in 14 chance of a used BCM matching your key.

I doubt that the gauge problem is power related. The voltmeter uses the same power as the other gauges so since it works you must have power. But the voltmeter is the only one that doesn't require a data signal (it only needs power and ground). That suggests that the problem is with the class 2 serial data connection from the PCM (there is no network like there is in newer vehicles).

eallanboggs

iTrader: (1)

16 pin data link connector. each pin has an assignment. when I have a few minutes I post the pinout for you.

01ssreda4

iTrader: (96)

I first probed every fuse with the multi-meter, verifying that with the car on, the fuse showed 12+ on both sides. Then out of frustration later, I pretty much pulled every one that could possibly be linked to the gauges and physically looked at it. No issues were seen either way.

That was exactly my thinking. My original suggestion was to try a known good computer and see what happens. Is this out next step.????

BTW I forgot to mention, in the computer (with HPTuners) the VATS is turned off.

AH....Another detail I left out, the temp, and gas level go all the way to the left, the oil pressure gauges pegs out all the way to the right........it does this each time you turn the ignition on, if they have moved off their spot some, when you hit the ign, they will energize and move to where they sit.

WhiteBird00

iTrader: (4)

VATS can not be disabled in programming. The PCM is programmable so you can program it to ignore the fuel enable signal normally required from the BCM. But the BCM is not programmable so there is no way to eliminate VATS in the BCM which means that you will not get ground to the starter relay unless you bypass VATS or provide a different ground to the relay.

01ssreda4

iTrader: (96)

I have heard this also.......so what do we do??

Btw, speedo and tach are dead, but I believe the odo is lighting up, Hilton can verify this....

Hilton

iTrader: (36)

Yes, the odo and trip are lighting up, they're just not increasing in mileage as I drive.

eallanboggs

iTrader: (1)

DLC pinout:
pin2 J1850 Bus+
pin4 chassis gnd
pin5 sensor gnd
pin6 CAN high
pin7 K line
pin10 J1850 Bus-
pin14 CAN lo
pin15 L line
pin16 12Vdc Batt
You need a DSO or GMM to see activity on the bus(CAN hi and CAN lo). You won't know what all the handshakes mean, but you will be able to either: see activity, see bus held hi or bus held lo. You want to see activity on the bus even if you don't know what it means. You can check power and ground with your DVOM. There are two rows of pins. One row is narrower than the other. Starting with pin1 on the left if the narrower row is on the bottom(the narrower row is sometimes on the top depending on the manufacturer) to pin8 on the right. Pin 9 is on the left side of the wider row(again requiring that the wide row be on the top) to pin 16 on the right.

WhiteBird00

iTrader: (4)

The easiest thing is to just cut and ground the yellow/black wire from the starter relay. That will provide a constant ground to the relay coil rather than one that is controlled by the BCM.

The other option is to do a VATS bypass using resistors to make the BCM think the correct key is always being used. You can find directions by searching "VATS bypass" in the electronics section.

BTW, have you checked that the connector on the back of the cluster is firmly seated? The problem sounds like a bad data link connection and that would be the first place to look.

01ssreda4

iTrader: (96)

I installed remote starters for several years so I am very familiar with bypassing vats using resistance to trick the computer into letting it start.

The whole problem started in this order: Motor was replaced, everything functioned correctly, then after tranny problems, I went through the T-56 and fixed it, clutch was replaced and nitrous system was removed from the car. Then upon initial crank up, the starter would turn over. A jumper wire was applied to the 30 and 87 terminals of the starter relay and the car would crank and run perfect. I grounded the yellow/black wire so that it could be started using the key.

So this is where we are at. I dont believe that any wiring from the nitrous removal caused this although its funny how is corresponded directly after.

SuperC1

iTrader: (4)

I'm having the same issue, when I turn the key I can hear the fuel pump prime, but no dash lights, plus it won't crank. I never did hear the relays click either, but all the fuses are good. I swapped the relays around and still nothing, so I'm guessing the relays aren't geting any fire when the switch comes on. I checked all the fuses with a test light and they are getting fire even the ones that come on with switched power, but no dash light or CEL. The funny thing about all of this is the car was running when I noticed the failure. I had just made a pass at 120mph before and was driving home when this all happened, go figure. The main thing that got my attention was the oil pressure was pegged out, but when the car is off it never goes back to zero, so I figured the guage or cluster was just going bad.

eallanboggs

iTrader: (1)

You can temporarily bypass a relay by jumping from pin 30 to 87(LOAD side) for test purposes. If you have power at 30 then jumping to 87(N.O. contact) simulates the relay working properly during the test. This allows you to say OK if this is working what is the result and you can narrow down your search. You can do this with any relay. You can also jump from 85 to 86 to simulate the coil(control side) of the relay. If you jump from 30 to 87 and the circuit works, but then it doesn't work without the jumper you have to look at the control side (85 to 86). You then ask youself if you have power and ground to the control pins at the proper time to energize the relay. You must have a schematic during these point to point tests.