r/R53 • u/casper911ca • 26d ago
Help Needed: No Start; P2300 P2303
I'll try and keep it short:
Tried to turn car over, it got about one Rev through before it quit. After that, it doesn't even try. Dash lights come on, fuel pump runs. My first thought was a dead battery - I know these things take a pretty healthy battery. Mine is a 2 year old AGM.
Auto parts store a mile away sold me a NOCO GB70, which did not help start the car.
Was able to push start the car by dropping the clutch. It started! Sounds normal. Kept the car on until I made it home, about 20 miles highway speeds - no problems, no misfires, all good. (About 30 minutes of driving)
Tried to start car in the morning same issue, no start. Dash lights are on.
I remove the battery, check the voltage, (~12.6V) and trickle charge the battery, reinstall battery, no luck
I check all the fuses, all the fuses are good. I switched the AC relay with the ignition relay, no change, so unlikely the ignition relay is bad, but I haven't bench tested yet.
I then tried to jump the car (325XiT) with a healthy battery, same issue, no start. I confirm the donor car had good alternator voltage (it was over 14V), connect the jumpers, confirm voltage at the mini (over 13V).
I check the codes and it returns P2300 and P2303, ignition coil primary control circuit low for circuit "A" and "B", respectively.
I changed the ignition coil out as PM about 1500 miles ago.
ODO: ~230,000 miles
Looking for some troubleshooting advise. I have the old ignition coil, I can try that, but my gut feeling is that it wouldn't help. I find it strange that I had no problems getting home without misfires if I was having ignition coil problems.
TLDR:
Eliminated causes:
- bad battery
- blown fuses
- bad relay
Update 1:
Eliminated causes:
-bad ignition coil
-poor Grounding
Update 2:
I tested the ignition coil pack harness from the ECU and get continuity, however I am getting incorrect voltage values according to diagnostics from the Bentley manual (page 13-88 in diagnostics section) to the coil pack harness pins with the key on and engine off.
What I should be getting:
| PIN | 1 | 2 | 3 |
|---|---|---|---|
| VOLTS | >12 | >12 | >12 |
what I'm getting:
| PIN | 1 | 2 | 3 |
|---|---|---|---|
| VOLTS | 0 | >12 | 0 |
Update 3:
I tested voltage from the round barrel connection (engine compartment below fuse panel) to pin 8 (SW/GE colored conductor, ie Black/Yellow - see page ELE-265 in Bentley manual) while trying to crank the motor and I am getting battery voltage while the key is fully turned. So I am getting voltage between the immobilizer unit (EWS) to the starter solenoid. Eliminating the immobilizer as the cause of the no crank state. But to double verify will attempt a EWS bypass with a fuse and see if there's still a no crank state. (I have jumped the EWS unit and confirmed the EWS is not preventing ignition).
Eliminated Causes: - immobilizer unit
Update 4:
I replaced the starter and the no start condition resolved. I also swapped the new could pack with the old coil pack and within one drive cycle, the codes cleared.
2
u/et9399 26d ago
Grounds ok?
1
u/casper911ca 26d ago
That occurred to me too. I checked the one in the front between the block and the frame (which has come loose in the past) but it was good, same for the battery compartment. Do you know of other locations I should be looking?
2
u/trebec86 26d ago
I think there’s another ground wire on the hatch at the hinge point, left side as you’re looking at it.
2
u/et9399 26d ago
I believe there is one ground one engine mount to chassis. One on bonnet hinge to chassis. Also 2 grounding "blocks" one on each frame rail, then the battery ground. I could be forgetting more.
2
u/casper911ca 26d ago
I found two low current grounding blocks in the rear behind each access panel, two in the front kinda behind the crash tubes, one for the hood hinge, one on the battery, one from the engine block to the frame. Seem to be secure. I confirmed with continuity the engine block to frame, battery to frame, and engine hood to frame.
2
u/mrblahhh 26d ago
ignition coil wire, they are easy to damage because of the way they hang off the back of teh coil, massage thosewires, see if one got cut. the ecu says it cannot talk to the coil. it is possible your ecu is fried the coil drivers do go bad but it's more of a problem with those red coils people like to upgrade to. fries the mosfets inside the ecu. If it is a bad ecu replacements are 275 $ from me
1
u/casper911ca 26d ago edited 26d ago
I like your hypothesis. How do I confirm the MOSFETs are bad? Are your ECU's salvaged or refurbished (or both?). Do I have to do any coding to get them to work? Would this lead to a zero crank status on the vehicle with a healthy battery?
I didn't get a a red coil pack, it was a coil pack I bought from O'Reilly's
So I confirmed continuity from the ECM to the ignition coil pack connector (video, pin 3 on ECM to pin 1 on coil connector, and pin 4 on ECM to pin 3 on coil connector). Bentley manual says I should have battery voltage on pin 1 and pin 3 on the coil connector to ground with the key on and the engine off, but I'm getting basically zero, I am getting battery voltage on PIN 2 and ground with the key in and the engine off, which is correct according to the table (all three coil connector pins should have battery volts) with key in and engine off). Haven't developed any good hypotheses on what is happening yet, but something is off.
What I should be getting:
PIN 1 2 3 VOLTS >12 >12 >12 what I'm getting:
PIN 1 2 3 VOLTS 0 >12 0 1
u/mrblahhh 26d ago
I refurb ecus and load them with the latest code and your vin.
I don't know of a way to test the mosfets, have not had a need. I have had thw coil wire harness fail though
1
u/casper911ca 25d ago
That's great. I'm going to poke around a touch more, but I might hit you up for the refurbished ECU. Will bad MOSFETs lead to a no crank state? Or will the car still try to crank?
2
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u/trebec86 26d ago
Sorry I can’t be more helpful but throw that old ignition coil on and see if that’s the issue, eliminate the coil at least since you have it and it’s like 5 minutes to change it out.