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No start condition, P0118 and P0343 codes

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,269 POSTS
Hi,

If you have a short, then yes, you can run a new line. But, if you have a short to power when you have both ends disconnected, you will need to eliminate that because you will have a hot wire cut at both ends which is shorted to power somewhere in the middle. (Does that make sense?)

Joe
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Friday, April 17th, 2020 AT 4:49 PM
Tiny
RGRUBER69
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Makes perfect sense! If I (and this is a big if) I did go that route and run all new wires from ECM to sensors, I would of course cap all cut wires at the ends. But I do want to do this the right way, electrical has never been my strong suit and I'm trying to wrap my head around how best to verify what wires are shorted. That's so much wire loom and tape to cut through! And so many places I can't get to without disassembling parts of the engine!
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Friday, April 17th, 2020 AT 5:16 PM
Tiny
RGRUBER69
  • MEMBER
  • 22 POSTS
Makes perfect sense! If I (and this is a big if) I did go that route and run all new wires from ecm to sensors, I would of course cap all cut wires at the ends. But I do want to do this the right way, electrical has never been my strong suit and I'm trying to wrap my head around how best to verify what wires are shorted. That's soooooo much wire loom and tape to cut through! And so many places I can't get to without disassembling parts of the engine!
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Friday, April 17th, 2020 AT 5:16 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Exactly! I rarely replace harnesses any more or tear them apart. When done right as Joe described it is much easier and cleaner to run a new one and secure it. Let us know how you make out. Thanks
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Saturday, April 18th, 2020 AT 7:01 PM
Tiny
RGRUBER69
  • MEMBER
  • 22 POSTS
I'm no closer to understanding what exactly happened. I've rewired all my sensors from the ECM to the sensors, MAF, coolant, cam, vapor canister, intake. I'm still getting 10v on my low ref lines when MAF sensor is plugged in, 0v when unplugged and my coolant sensor reading is still at -40 either way. When I first rewired the low reference lines, everything read fine until the next morning when I went out to cleanup the new wires, I double checked my readings and that's what I was getting. At this point I don't know what else to do or check! New sensors, new harnesses, new wires, no change. No more pending codes or stored codes, still no start condition. Help!
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Saturday, April 25th, 2020 AT 11:02 AM
Tiny
RGRUBER69
  • MEMBER
  • 22 POSTS
Okay, not sure if this will help or make any sense, but I've ran new 12v wire from fuse panel to my cam sensor. When I disconnect that wire at the fuse panel, I get normal 5v on the low ref. And by coolant temperature reads -14. Weird, and as stated, I'm getting way more confused with everything I do!
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Saturday, April 25th, 2020 AT 4:56 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,269 POSTS
Hi,

I am getting more confused as well. LOL The sensor should have 12v from the ECM. If I understand, you ran a jumper wire to 12v from a fuse to the cam sensor. Is that when you had closer to the correct voltage from the low reference and the -14° F from the coolant temperature sensor? What is the actual temperature?

Let me know.

Take care,
Joe
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Sunday, April 26th, 2020 AT 7:33 PM
Tiny
RGRUBER69
  • MEMBER
  • 22 POSTS
I cut the 12v wire to cam sensor at the fuse panel, ran a new 12v line. But checked all my readings before hooking up the new wire. That's when I had the -14 and correct voltage at low ref. With No 12v hooked up at cam sensor. Actual temperature was about 65°.
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Monday, April 27th, 2020 AT 2:01 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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If you look at picture 1, it shows where the power supply to the cmp comes from. You replaced that. Next, note that one wire splices (I circled it) to the low ref. That low reference is used by the coolant temp sensor and the MAF sensor. Since you get the same thing when you run power direct but chances when you remove the power to the CMP, something is likely back feeding power to MAF. Disconnect the MAF sensor and see if it changes the reading when you power the CMP.

Let me know.
Joe
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Monday, April 27th, 2020 AT 11:28 AM
Tiny
RGRUBER69
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I've completely removed the splice pack circled and replaced all low ref wires from the ECM to each sensor, creating a new splice at the ECM side. The 12v power to the CMP and MAF have been replaced from the fuse panel harness to the sensors, along with all the other wires in each harness, at the ECM.
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Monday, April 27th, 2020 AT 12:34 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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I am going to ask for another tech's opinion, but in all honesty, I suspect something to be wrong with the ECM.

Lets see what he says.

Joe
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Tuesday, April 28th, 2020 AT 7:31 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,959 POSTS
Hello,

Yes, it sounds like the drivers inside the PCM have gone bad, probably due to the shorted wiring. I would try a rebuild unit please give your VIN number when ordering. Here are the instructions on how to replace the unit in the diagrams below. Yours should have this done before you get it.

Before Programming a Control Module (shop)

IMPORTANT: DO NOT program an existing control module with the identical software/calibration package. This procedure is not a short cut to correct a driveability condition. This is an ineffective repair. A control module should only be programmed when the following occurs:
- When a service procedure instructs you to replace the control module. The service part control module does not contain operating software or calibrations.
- General Motors Corporation releases an updated software/calibration package.

Ensure that the following conditions are met before programming a control module:
- Vehicle system voltage:
- There are no charging system concerns. All charging system concerns must be repaired before programming a control module.
- The battery voltage is greater than 12 volts but less than 16 volts. The battery must be fully charged before programming the control module.
- A battery charger is NOT connected to the vehicles battery. Incorrect system voltage or voltage fluctuations from a battery charger may cause programming failure or control module damage.
- Turn OFF or disable any system that may put a load on the vehicles battery. Turn OFF or disable systems such as:
- Daytime running lights (DRL). Applying the parking brake, on most vehicles, disables the DRL system.
- Heating, ventilation, and air conditioning (HVAC) systems
- Cooling System fans, etc.
- The ignition switch is in the proper position. The scan tool prompts you to turn ON the ignition, with the engine OFF. DO NOT change the position of the ignition switch during the programming procedure unless instructed to do so.
- All tool connections are secure:
- The RS-232 cable
- The connection at the DLC
- The voltage supply circuits
- The OBPA
- DO NOT disturb the tool harnesses while programming. If an interruption occurs during the programming procedure, programming failure or control module damage may occur.
- If you are performing the pass-through programming procedure using a notebook computer without the power cord, ensure that the internal battery is fully charged.

After Programming a Control Module
The powertrain may operate slightly different after a control module software/calibration update. Operating the powertrain through various driving conditions allows the control module to re-learn certain values. The control module must re-learn the following after a software/calibration update:
- Fuel trim correction
- Idle air control (IAC) learned position
- Automatic transmission shift adapts

Other learned values only re-learn by performing a service procedure.

If a control module is replaced the following service procedures may need to be performed:
- The crankshaft variation learn procedure
- The engine oil life reset procedure
- The idle learn procedure
- The inspection/maintenance complete system set procedure
- The vehicle theft deterrent password learn procedure
- The throttle position (TP) sensor learn procedure

Check out the diagrams (below). Please let us know what happens.
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Tuesday, April 28th, 2020 AT 7:46 PM

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