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Hi all, have a 06 HHR 2.2 L61 engine. had code P0340 come on everytime I cleared it then started engine. it had a long crank and I scanned I all the parameters many times, everything checked out ok. ran great after starting. I replaced the coil pak,boots,plugs,and ignition control module and crank sensor. no luck,check engine light still on with long crank. I found an open wire from the ignition control module to the ECM. it's the brn/yellow wire to pin # 72 on the C1 connector of the ECM. it was open after load testing it. I jumped around it with a 16ga. wire and put it into a clam shell conduit. that took care of the P0340 and the check engine light. turns out the ignition control module uses the crank sensor to send the ECM the position of #1 piston so it can fire the injectors at proper time. it was using piston # 3 since it did not have the correct info. I made a test light to load it with a headlight bulb and jumper wires. hooked one end of the light to pin # 72, the other to battery + and I grounded the brn/yellow wire at the ignition control module. it was open. Im a retired ASE master tech and this one had me pulling the little hair I have left out. I hope this helps others who are having this same code issue . I have seen a lot of post on the net about the P0340 , seems a lot of people are having this problem on the 2.2 chevy engines, the newer 2.2's that have VVT will not have this setup. they will have cam sensors.
Last edited by Oldblue; 03-02-2023 at 11:59 AM.
Reason: Corrected code
I didn't see what fixed your P0340.
Pin #72 on the ECM is low ref. I am guessing that your wires have yellowed with age and you mean the brown/white CMP signal wire on pin #71 on the ECM.
Low ref is sort of digital ground or 0v. It would show as open.
So, I guess what you could have done is to inspect and repair the pins on the connectors. Replacing the ICM usually fixes it maybe, because it fixes the connector.
Only 2006 HHR had this ignition system (wasted spark) later years have CoilOnPlug. In wasted spark cylinders 1 & 3 and 2 &4 fire at the same time regardless of cycle.
Your understanding of the ICM is a bit flawed:
Hi donbrew. yep,your right, I just forgot the tracer color. it is wht. Im using Mitchall on demand, when the cmp wire is damaged or open the ign module will steal the info from the remaining cylinders according to my scanner. it was using cyl # 3 for a reference. it still ran,and ran good,just caused a long crank and a 340 code. ran the new wire and no more long crank and no more code 340.
The attachments I included are from Mitchell OnDemand, different from your understanding.
The ICM compares #1 and #3 to calculate which one fired on the compression stroke. The CMP signal tells the ECM which one was wasted. Either no signal or no change in the signal triggers the P0340.
If the ICM is producing a changing signal and the ECM is not receiving it there is probably a loose pin in a connector
I got no idea how you figured anything about stealing signals. The ICM uses both.
The attachments I included are from Mitchell OnDemand, different from your understanding.
The ICM compares #1 and #3 to calculate which one fired on the compression stroke. The CMP signal tells the ECM which one was wasted. Either no signal or no change in the signal triggers the P0340.
If the ICM is producing a changing signal and the ECM is not receiving it there is probably a loose pin in a connector
I got no idea how you figured anything about stealing signals. The ICM uses both.
Don, whats your problem? I did the diagnoses on my car, studied the theory on the ignition module to the ECM, it FIXED my problem,thought I would share it with others that have the same problem. if you do not want the info then disregard it and move on, no reason for an interrogation.
Don , I don't know what else to say,I did the the diagnoses and repaired it. it works great. I had this car for 30 days, the light was on when I bought the car,the seller told me he had done everything he could come up with and the code was back at every startup after clearing. what I read in MOD was the theory or description of the ignition control module. it says the ignition control module gets the crankshaft position from the crank sensor and sends the info (input) to pin # 72 on the ECM. I spent 13 years of my 52 years turning wrenches rebuilding industrial & automotive starters and alternators and Electrical wiring shorts and repair. I load tested the brn/wht circuit. it was open. I replaced the wire,the circuit tested complete and closed,started it up after clearing the light,it has not come back on. however it did start over heating,checked that out, blown head gasket. so have to say head is in the machine shop now. seller told me he put a head gasket on it and had the head resurfaced. he lied. the head was not machined,it did have loads of copper spray on it and was cleaned. with the parts I have ordered for it,new timing & balance shaft kits,water pump & radiator and hose's I almost wish I did not buy this. but I have to make sure it will be dependable for my wife. before finding the open circuit,I bought a plug & play ECM for it, I found the problem before it got here,so I will keep for a spare. ps, after driving it for a week back and forth to work she ran it into the back of a pick up truck. , so, found a hood,grill,front bumper assembly of the same color and have them on. did I mention I retired?? only from a paycheck..
03-02-2023, 10:23 AM
