If the relay is not working have you checked 86 and 85 ??...do you know how to check that "control" side ??...do you have power on terminal 86 and is the ECM grounding 85 ??...do you know how to check this ??...a relay "clicking" means nothing...when you say the "ECU is undiscovered" do you mean the scan tool will not communicate with the ECM ??...I'm a stickler for correct terminology...after checking this ignition feed have you checked the battery feed and ground for the ECM...no power and ground NO communication.

 

I have confirmed the 86 to 85 works fine as I tested them with a battery and with power coming out of the fusebox. The high amp side works fine too as if the relay is clicked that circuit closed and would send power to the fuse 4. I dropped wires into 86 and connected them to the correct side of the relay and grounded it off of my alternator, It clicked closing the high amp circuit. I then dropped a wire into the 85 side and connected it to the correct node on the relay and it would not click when I touched 86 with the hot wire. The relay works fine, just doesn’t seem to jive when it is inserted into the box. I narrowed it to the ground side being unhappy. That issue is interesting to me.

ECU being dead is U0100, again, OBD2 cannot talk to ECU. Same issue as before, just with troubleshooting and more info, but no dice

 

You are doing way to much work to be checking that relay...should take 5 minutes to check 4 terminals for the relay...so you're saying the ECM is not providing ground at terminal 85 ??...with test light connected to battery POSITIVE when ignition is on the light should illuminate when probing 85 at the relay....have you checked G100 which is the ground for the ECM ??

 

Mmm, maybe I am overkilling the relay, but I am doing my best to be thorough. Are you saying that 85 of the ECM relay is grounded by the ECM and not the car’s ground? After a second look at the diagram, this does appear to be the case. What ECU pin is G100? Is that X2-73?

 

There are 2 grounds for the ECM...terminals 73 on both X2 and X3...that is important as that will be one of the grounds for the relay.

 

The cars ground is G100 and that will provide the ground for the relay...the ECM has no special ground inside of it just for relays and such.

 

Yea, I saw that X2 and X3 pin 73 were for power ground and signal ground respectively. Good info, I will keep poking at it as well as I can and report back

 

The only thing that changed aside from the ECU is a lethal garage e85 sensor. It was reading alcohol level fine with the tuned ECU in it, so I wouldn’t expect it to cause any issues. But regardless, it gets power from the PCV plug on the intake and I followed their instructions and grounded it on a valve cover bolt. Would that affect this in any way? I have been out of town, so have not inspected my g100 on the passenger side of the block. What other grounds should I inspect while I am in there?

 

OK, so this is what I found. I have pulled all three connectors off of the ECU to test the grounds and power. I ran a jumper cable from the positive of my battery and tested terminal 73 of X2 and X3. My test light lit up, I don’t have a way to load this though and view the voltage drop other than the test light. Aside from that, I jumped the ECM relay and touched terminal 73 of X1 with my test light that was grounded to my alternator and it also lit up. So at this time from what I can tell the ECU should be getting power, and the signal and power are grounded. Something that is still interesting to me though is that I could not successfully get a test light to light up when checking the 85 side of the ECM relay. Do you know why I cannot get my test light to light up from the 85 side of that relay? I also did jack up the car and run my positive jumper cable to G 100, the bolt on the passenger side of the block and my test light did light up so it appears to be grounded well

 

ECM relay ???...terminology is important so which relay are you referring to ??...can you point it out ??

 

The relay upstream of fuse 4, also known as KR75 or number 62 in the fuse box. The big grey bastard in this picture

 

Are you attempting to start the car when checking terminal 85 at the relay ??...the ground is not present at all times...if the test light does not illuminate you will have to check AT the ECM...you can have a broken wire between the relay and ECM... I'd check terminal 72 on the X1 connector by back probing...if still no good may be a bad ECM.

 

You know before I even get into power and grounds, when I have a CAN lost communication code the first thing I do is check the CAN Bus wiring. No CAN Bus, no communication. ECM is the terminating node so even with GM's "Daisy Chain" topology you can have the bus severed and it (the Bus) will still function for other modules

 

The car is in run mode when I am checking the ground of that relay. I was unaware that the ground can sometimes be there and sometimes not. Should I be checking X1-72 when the car is in run mode as I have been, or should I test it with the car off? IIRC I checked X1-72 last week and it lit up when the car was off but not when the car was in run mode. I will double check this, but this is in my memory

Regarding the CAN wiring, where would I start with testing that?

 

Usually a simple continuity test is all that's required. I would find the next module up the chain and do it from there. The other thing since it is a terminating node is on the module pins see that you are getting 120 ohm across them. There is a terminating resistor and if it has an issue it can cause problems.

 

Do you know what the upstream module would be? Also, you mentioned checking the ECMs pins for resistance, do you know which ones in particular I should hit with the multimeter?

 

Below are the flow charts for your P0615 and 0617...I doubt it is a broken wire as had been mentioned since your concern is intermittent...to check the "physical layer" of the bus there is no need to go upstream of the ECM which would be your Power Steering Control Module...you can quickly check by disconnecting the battery and with your ohmmeter across terminals 6 and 14 at the DLC you should see approximately 60 ohms...if you see 60 ohms the CAN bus wiring is good up to and through the ECM CAN bus transceiver from the DLC.

P0615 Circuit/System Testing

1. Ignition OFF and all vehicle systems OFF, disconnect the KR27 Starter Relay. It may take up to 2 min for all vehicle systems to power down.
2. Test for less than 10 Ω between the ground circuit terminal 85 and ground.
   • If 10 Ω or greater
   1. Ignition OFF.
   2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
      
      
   • If less than 10 Ω
3. Ignition ON.
4. Verify a test lamp illuminates between the B+ circuit terminal 30 and ground.
   • If the test lamp does not illuminate and the circuit fuse is good
   1. Ignition OFF.
   2. Test for less than 2 Ω in the B+ circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is OK and there is voltage at the fuse.
      
      
   • If the test lamp does not illuminate and the circuit fuse is open
   1. Ignition OFF.
   2. Test for infinite resistance between the B+ circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance,
   3. Disconnect terminal 1 X1 from M64 Starter Motor.
   4. Test for infinite resistance between the control circuit terminal 87 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the KR27 Starter Relay.
      
      
   • If the test lamp illuminates
5. Connect a test lamp between the control circuit terminal 86 and the ground circuit terminal 85.
6. Verify the test lamp turns ON and OFF when commanding the Starter Relay ON and OFF with a scan tool. If command is unavailable, verify by setting parking brake, press clutch (for manual), activate ignition CRANK to ON and OFF.
   • If the test lamp is always OFF
   1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
   2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
   3. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K20 Engine Control Module.
      
      
   • If the test lamp is always ON
   1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module, ignition ON.
   2. Test for less than 1 V between the control circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K20 Engine Control Module.
      
      
   • If the test lamp turns ON and OFF
7. Ignition ON, connect a 30 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87.
8. Verify the M64 Starter Motor is activated.
   • If the M64 Starter Motor does not activate
   1. Ignition OFF, disconnect the harness connector at the M64 Starter Motor.
   2. Test for infinite resistance between ground and terminal X1 A or X1 1.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
   3. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the M64 Starter Motor.
      
      
   • If the M64 Starter Motor activates
9. Test or replace the KR27 Starter Relay.

Component Testing

Relay Test

1. Ignition OFF, disconnect the appropriate relay.
2. Test for 70–150 Ω between terminals (85 or 1) and (86 or 2).
   • If less than 70 or greater than 150 Ω
     Replace the relay.
   • If between 70–150 Ω
3. Test for infinite resistance between the terminals listed below:
   • (30 or 3) and (86 or 2)
   • (30 or 3) and (87 or 5)
   • (30 or 3) and (85 or 1)
   • (85 or 1) and (87 or 5)
   • (86 or 2) and (87 or 5)
   • If less than infinite resistance
     Replace the relay.
   • If infinite resistance
4. Install a 3 A fused jumper wire between relay terminal (85 or 1) and 12 V. Install a jumper wire between relay terminal (86 or 2) and ground.
5. Test for less than 5.0 Ω between terminals (30 or 3) and (87 or 5).
   • If 5.0 Ω or greater
     Replace the relay.
   • If less than 5.0 Ω
6. All OK

DTC Descriptors

DTC P0615Starter Relay Control Circuit
DTC P0616Starter Relay Control Circuit Low Voltage
DTC P0617Starter Relay Control Circuit High Voltage

Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance Relay Switch B+ Terminal 30 1 2 — — Relay Coil Ignition Terminal 86 P0616 P0615 P0617 — Relay Switch Control Terminal 87 2 2 3 — Relay Coil Ground Terminal 85 — P0615 — — 1. Opens fuse, Starter Solenoid does not click.
2. Starter Solenoid does not click.
3. Cranks all the time.

Circuit/System Description

When the ignition is activated to start the vehicle, a discrete signal is supplied to the body control module (BCM). The BCM then sends a message to the engine control module (ECM) that crank has been requested. The ECM then verifies that the clutch pedal is depressed or the transmission is in Park/Neutral. If it is, the ECM then supplies 12 V to the control circuit of the starter relay. When this occurs, battery voltage is supplied through the switch of the starter relay to the starter solenoid.

Conditions for Running the DTC

• The ignition is activated to START.
• The system voltage is between 9.5–18 V.

Conditions for Setting the DTC

The ECM detects improper voltage on the control circuit of the starter relay.

Action Taken When the DTC Sets

DTC P0615, P0616, and P0617 are type C DTCs.

Conditions for Clearing the DTC

DTC P0615, P0616, and P0617 are type C DTCs.

Reference Information

Schematic Reference

Starting and Charging Schematics

Connector End View Reference
Component Connector End Views

Description and Operation
Starting System Description and Operation

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference
Control Module References for scan tool information

Circuit/System Testing

1. Ignition OFF and all vehicle systems OFF, disconnect the KR27 Starter Relay. It may take up to 2 min for all vehicle systems to power down.
2. Test for less than 10 Ω between the ground circuit terminal 85 and ground.
   • If 10 Ω or greater
   1. Ignition OFF.
   2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
      
      
   • If less than 10 Ω
3. Ignition ON.
4. Verify a test lamp illuminates between the B+ circuit terminal 30 and ground.
   • If the test lamp does not illuminate and the circuit fuse is good
   1. Ignition OFF.
   2. Test for less than 2 Ω in the B+ circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is OK and there is voltage at the fuse.
      
      
   • If the test lamp does not illuminate and the circuit fuse is open
   1. Ignition OFF.
   2. Test for infinite resistance between the B+ circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance,
   3. Disconnect terminal 1 X1 from M64 Starter Motor.
   4. Test for infinite resistance between the control circuit terminal 87 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the KR27 Starter Relay.
      
      
   • If the test lamp illuminates
5. Connect a test lamp between the control circuit terminal 86 and the ground circuit terminal 85.
6. Verify the test lamp turns ON and OFF when commanding the Starter Relay ON and OFF with a scan tool. If command is unavailable, verify by setting parking brake, press clutch (for manual), activate ignition CRANK to ON and OFF.
   • If the test lamp is always OFF
   1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module.
   2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
   3. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K20 Engine Control Module.
      
      
   • If the test lamp is always ON
   1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module, ignition ON.
   2. Test for less than 1 V between the control circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K20 Engine Control Module.
      
      
   • If the test lamp turns ON and OFF
7. Ignition ON, connect a 30 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87.
8. Verify the M64 Starter Motor is activated.
   • If the M64 Starter Motor does not activate
   1. Ignition OFF, disconnect the harness connector at the M64 Starter Motor.
   2. Test for infinite resistance between ground and terminal X1 A or X1 1.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
   3. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the M64 Starter Motor.
      
      
   • If the M64 Starter Motor activates
9. Test or replace the KR27 Starter Relay.

Component Testing

Relay Test

1. Ignition OFF, disconnect the appropriate relay.
2. Test for 70–150 Ω between terminals (85 or 1) and (86 or 2).
   • If less than 70 or greater than 150 Ω
     Replace the relay.
   • If between 70–150 Ω
3. Test for infinite resistance between the terminals listed below:
   • (30 or 3) and (86 or 2)
   • (30 or 3) and (87 or 5)
   • (30 or 3) and (85 or 1)
   • (85 or 1) and (87 or 5)
   • (86 or 2) and (87 or 5)
   • If less than infinite resistance
     Replace the relay.
   • If infinite resistance
4. Install a 3 A fused jumper wire between relay terminal (85 or 1) and 12 V. Install a jumper wire between relay terminal (86 or 2) and ground.
5. Test for less than 5.0 Ω between terminals (30 or 3) and (87 or 5).
   • If 5.0 Ω or greater
     Replace the relay.
   • If less than 5.0 Ω
6. All OK

 

We do NOT check the ECM pins for resistance !!...the circuit must be dynamically tested....if you read this flow chart that is WRONG also as they the OE use resistance measurements...these engineers if they are electrical ones need to go back to basic electrical class !!!...I see members on here all the time doing it and the only time I'll take a resistance measurement is checking for that 60 ohms....did you watch the video in post 15 ???

 

Yea, I watched the power and grounds video. Its steps are what I followed to check the ECM connectors. While the starter issue codes were relevant, that no longer is the main issue as my ECM is still not communicating.

To restate my current position. X1-73 (only if I jump its relay) and X1-70 have 12V power when the car is in run mode. X2-73 and X3-73 have ground, as I stated previously, I ran a jumper cable off my positive terminal to my test light which lit up when touching them. I do not appear to have ground on terminal 85 of KR75 when the car is in run mode, but this may be expected as you have stated that ground is not always present.

Once I get off work, I will check my OBD plug at pin 6 and 14 for 60 Ohms. So currently, the 2 things I think it could be are 1) bad ECM or 2) good ECM, bad data line. More input and other potential directions would be appreciated though.

 

I would check terminal 85 AT the ECM...just plug everything back in and attempt to start the car...85 is "ground side switched" meaning the ECM provides the ground....back probe that terminal at the ECM...may be a broken wire between the ECM and the relay...if no comm yes see if you see 60 ohms battery disconnected...if all powers and grounds good may be a bad ECM...are there any data PIDS you can look at with your scan tool...is it a factory level one ??....see if you see a "CRANK REQUEST" input on the scan tool...who programmed this new ECM ??