No starter, no gauges, OBD2 not working either
01-13-2010, 12:18 AM
#21
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If you put the scanner interface into a USB port different than the one you initially used to program your laptop it won't recognize the cars computer. You need to scroll through on the initial interface page and scroll through the ports and keep trying until the computer recognizes the port. Most default to port #1.
01-13-2010, 12:43 AM
#22
You need to find out why your scan tool won't connect. Is your network down? Have you checked the pins on your DLC? If you have power and ground start looking for network activity using a GMM or DSO. You don't need to know what you're looking at. You only need to be sure you see activity on the line.
01-13-2010, 07:48 AM
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You need to find out why your scan tool won't connect. Is your network down? Have you checked the pins on your DLC? If you have power and ground start looking for network activity using a GMM or DSO. You don't need to know what you're looking at. You only need to be sure you see activity on the line.
01-13-2010, 08:47 AM
#24
The DLC should have Vcc regardless of whether the key is on or not. The DLC usually shares the cig liter fuse on GM so check that fuse first. You need to go back to basics starting with at the key switch using a schematic and a DVOM. Find out which circuits are HOT with the key off and at KOEO and KOER. Do some probing at your fuse panel and at your DLC. You can check for power and ground using a DVOM. To find network activity you'll need a GMM or DSO. A plain jane oscilloscope will work too. You not trying to interpret the data you see. I don't think that information is even released by the manufacturers. All your looking for is activity which tells your network is OK. That it is not being held down to the ground by a short to the chassis or being held high by a short to power. A module could also hold the network down too. You may have to unplug modules one at a time until the network comes back online as you watch the scope for activity.
Last edited by eallanboggs; 01-13-2010 at 08:52 AM.
01-13-2010, 11:27 AM
#25
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The DLC should have Vcc regardless of whether the key is on or not. The DLC usually shares the cig liter fuse on GM so check that fuse first. You need to go back to basics starting with at the key switch using a schematic and a DVOM. Find out which circuits are HOT with the key off and at KOEO and KOER. Do some probing at your fuse panel and at your DLC. You can check for power and ground using a DVOM. To find network activity you'll need a GMM or DSO. A plain jane oscilloscope will work too. You not trying to interpret the data you see. I don't think that information is even released by the manufacturers. All your looking for is activity which tells your network is OK. That it is not being held down to the ground by a short to the chassis or being held high by a short to power. A module could also hold the network down too. You may have to unplug modules one at a time until the network comes back online as you watch the scope for activity.
01-13-2010, 12:45 PM
#26
If you can't connect to the net with the key ON you have to find out why your network is down. Do you have a wire shorted to ground or power holding the net low or hi? Do you have a defective module on the net pulling the entire net down? Time for a schematic and an oscilloscope, DSO or GMM unless you can afford a TechII which you might find on sale for $3,000.00. You might find a SnapOn Vantage for $300 on Ebay. You have to look for a short to power or ground on the net. If you don't find a short you have to unplug module connectors one at a time until you see activity start happening on the net. Will a different scan tool connect to the vehicle other than HPT? Have you tried connecting your HPT to another vehichle.
01-13-2010, 06:22 PM
#27
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If you can't connect to the net with the key ON you have to find out why your network is down. Do you have a wire shorted to ground or power holding the net low or hi? Do you have a defective module on the net pulling the entire net down? Time for a schematic and an oscilloscope, DSO or GMM unless you can afford a TechII which you might find on sale for $3,000.00. You might find a SnapOn Vantage for $300 on Ebay. You have to look for a short to power or ground on the net. If you don't find a short you have to unplug module connectors one at a time until you see activity start happening on the net. Will a different scan tool connect to the vehicle other than HPT? Have you tried connecting your HPT to another vehichle.
01-13-2010, 07:56 PM
#28
They're located all over the vehicle. You're going to need Helm, Alldata or Mitchell to find them and the connectors you need to unplug. You'll also need to determine the topology of your network. I would chose Helm of the 3 since they make the OEM manual.
01-14-2010, 07:32 AM
#31
Our cars don't have a network in the modern sense of the word. Several devices communicate with each other using class 2 serial signals in a single wire system.
The devices are:
- Powertrain Control Module (PCM), under the hood on right side of the firewall
- Instrument cluster
- Electronic Brake Control Module (EBCM), left frame rail attached to the brake pressure modulator valve
- Airbag Sensing and Diagnostic Module (SDM), under the center console
Each of these devices has a serial data wire going to a splice pack mounted just above the DLC (OBD2) port. It connects five wires together: dark green, dark blue, purple, light blue, gray.
The devices are:
- Powertrain Control Module (PCM), under the hood on right side of the firewall
- Instrument cluster
- Electronic Brake Control Module (EBCM), left frame rail attached to the brake pressure modulator valve
- Airbag Sensing and Diagnostic Module (SDM), under the center console
Each of these devices has a serial data wire going to a splice pack mounted just above the DLC (OBD2) port. It connects five wires together: dark green, dark blue, purple, light blue, gray.
01-15-2010, 12:56 PM
#32
01-23-2010, 03:28 PM
#35
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I have no one to blame but myself.
When I removed the nitrous from the car, the wires going to the engine bay were wrapped around the harnesses. Because I didn't want to cut the wires, I simply unplugged the harnesses and freed the wires.
I neglected to reconnect them.
When I removed the nitrous from the car, the wires going to the engine bay were wrapped around the harnesses. Because I didn't want to cut the wires, I simply unplugged the harnesses and freed the wires.
I neglected to reconnect them.
01-23-2010, 08:26 PM
#36
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robl Found the problem with the oil guage, pressure switch was unplugged.
Now, if can figure out the rest of my problem it would be great.
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.
Now, if can figure out the rest of my problem it would be great.
03-10-2010, 12:41 PM
#38
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Found out why my guages quit, the fuse was blown, so I replaced it and got power back but still no crank. I was able use my scan tool and pulled the codes and got a p0650 (mil malufunction). I still don't think this would stop it from cranking but for some odd reason it won't. I was told that if the guages fuse blew while the car was running it will not crank, but once the fuse was replaced everything should go back to normal, but this is not the case, what gives 
03-10-2010, 01:42 PM
#39
You need to go back to basics and treat the vehicle like it's NOT computer controlled. You should do point to point tests using a DVOM and good schematic. No Crank or No Start always starts at the BATT. All terminals must be clean and tight. The starter motor must be in working order and bolted tightly to the engine block(starter body and engine block is an electrical connection return path to BATT ground). Must also check key switch output when is start position. Does 12Vdc get to the starter relay when key is in S position? Have you jumped pin 30 to pin 87 at the start relay? Does the starter receive Ground from the ECM when the key is in the S position? You can simulate all the start functions by removing the starter relay and checking pins 85,86,87 and 30 when the key is in the S position. Use your schematic and DVOM to make these checks. This process applies to any starter circuit no just an LS series vehichle. The ECM may put ground on one side of the starter relay control circuit if all the conditions are satisfied for good start up. This might include being in Park or Neutral or having the clutch depressed on a manual trans.
Last edited by eallanboggs; 03-10-2010 at 01:48 PM.
03-10-2010, 04:08 PM
#40
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You need to go back to basics and treat the vehicle like it's NOT computer controlled. You should do point to point tests using a DVOM and good schematic. No Crank or No Start always starts at the BATT. All terminals must be clean and tight. The starter motor must be in working order and bolted tightly to the engine block(starter body and engine block is an electrical connection return path to BATT ground). Must also check key switch output when is start position. Does 12Vdc get to the starter relay when key is in S position? Have you jumped pin 30 to pin 87 at the start relay? Does the starter receive Ground from the ECM when the key is in the S position? You can simulate all the start functions by removing the starter relay and checking pins 85,86,87 and 30 when the key is in the S position. Use your schematic and DVOM to make these checks. This process applies to any starter circuit no just an LS series vehichle. The ECM may put ground on one side of the starter relay control circuit if all the conditions are satisfied for good start up. This might include being in Park or Neutral or having the clutch depressed on a manual trans.