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Old 06-24-2012, 06:46 PM   #1
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Default lack of check engine light problem

04 MSM 67k with FM intake and boost gauge.
The ecu had 2 codes: p2004 and p0031 (intake runner solenoid, bank1 o2 heater).

I think the 2004 is caused by where the person teed in the boost gauge and in a really dumb way (between that one way valve on the back of the intake) and I think I will have that fixed by relocating the gauge tee to the bov runner. The other, well I just got done replacing the front o2 and thats a pita.

I took the cluster out, replaced the bulb, no light. I didnt see anything that looked broken or cut in the electronics. I know the socket works because i swapped it with the abs one and that is fine. I dont see any moved or cut wires under the dash.

Car runs great, but no cel light when I turn on the ignition bothers me. Don't these cars show it or am I being dumb. What wire triggers the voltage to where the cel bulb is? I dont think I can pass inspection in NC without a working cel thouh I might be able to get a waiver.

Tips/tricks?
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Old 06-24-2012, 06:55 PM   #2
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aftermarket ecu?
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Old 06-24-2012, 07:33 PM   #3
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Doesn't look like it. The only wires that had been run anywhere near there were for the boost gauge's illumination.
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Old 06-24-2012, 07:35 PM   #4
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Anyone know which pin on the msm ecu that powers the cel? I could test it for continuity.
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Old 06-24-2012, 07:43 PM   #5
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Old 06-24-2012, 08:31 PM   #6
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p0031 fixed with so far after a short drive. 2004 came back, but I dont have the modified check valve, so I dont know if that will fix it or if I'll have to buy a solenoid.

Do I assume the same diagram applies to the 99, or the 01 because 04 is not included there.

I hadn't driven it in 24 hours. There was a little ticking on start, but it went away quickly. it must be the classic tick I read about. damn thing runs like a champ. those cars sure do warm up fast.
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Old 06-24-2012, 09:07 PM   #7
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Looks like white/blue and black/yellow are the two side to it. I traced the back of the cluster and they correspond to the same wires on the plugs. I guess this goes all the way to the ecu in the same colors?
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Old 06-25-2012, 12:33 AM   #8
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White/Blue should be on the middle of the three plugs. Check for breaks or splices and for continuity on the traces on the back of the cluster. If that checks out see is W/L will ground out when you turn the key on. It would be extremely unusual if the ECU was actually failing to report. Good luck and welcome on the other site too! When I saw this second post, I actually got off my a** and got the book to check.
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Old 06-25-2012, 01:42 PM   #9
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The ECU is reporting. Its just failing to turn on the light. I already pulled codes and pretty sure I fixed the p0031 with the o2 replacement. The p2004 needs to be fixed. I just tested the actuator with a vacuum pump and it reads within spec. I tested the solenoid with 12v and it also appears to be working within spec. Perhaps there is a leak that I havent found yet. What else can cause p2004?

I just checked the gauge cluster continuity. It appears that the blk/yel side has many points of contact but that goes back to the main fuse block somewhere. The wht/blu wire has continuity, and its the only wire that runs directly back to the pcm. I think the path of this communication is the problem. Next step is to pull the plugs on the pcm to look at those wires/leads.
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Old 06-25-2012, 02:35 PM   #10
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They definitely warm up fast... and the interiors do too. I'm retuning my buddies for bigger injectors right now. BTW, if you want the car to go faster, get a MS3 or at least a BEGi remap... you won't believe how much difference there is.
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Old 06-25-2012, 05:27 PM   #11
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ms3? Megasquirt?

I was thinking about a begi remap after I put another exhaust on it. Right now, all I want to do is make sure that its reliable and fix these gremlins. This cel issue is one hard f0ker to track down. I just went out and go a haynes book.
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Old 06-25-2012, 05:33 PM   #12
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Yeah, megasquirt 3 with ms3x preferably.
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Old 06-26-2012, 07:19 PM   #13
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http://www.bellengineering.net/templ...CU_diagram.pdf

This is for the 3 pin-row connectors. I know it says except msm, but I've traced the wire back to this very location based on the color coming from the gauge cluster and this confirms the function. Looks like a straight run with no other junction blocks in between based on other wiring diagrams. Perhaps somebody had a hydra in the car and tapped into this to the cel as a knock warning light or something and it got mangled....though I doubt it.

I'll have to test this tomorrow. 2R: ign on - below 1v and mil is on, idle - B+ (12v) and mil is off. The other wire is just a 12v bus and this is a switched ground system. Interesting, but I wanted to make 100% sure that I'm looking at the right wire.

The question is, if you cut it, does it incomplete the circuit and cause the mil not to work at all or stay on indefinitely? I'm thinking it would have to be cut somewhere because if it were grounded by something then the mil would never go off. There are no other points in the circuit where this could ground from the diagrams. Once the ign is on and the car is idle, it feeds it a 12v signal which again, just keeps the bulb off. Now to figure out where that cut is.
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Old 06-26-2012, 07:25 PM   #14
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Jumping the white/black wire to the yellow/black wire is a common "fix" for no CEL with an aftermarket ECU. It lights up with key on, and goes off after starting. Fools the inspector.

Usually this is done behind the glovebox. I'd look there.
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Old 06-26-2012, 07:34 PM   #15
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Mine doesnt come on at all, but I'll look behind the glove box. I'm going to ground the wire at the ecu and see if that produces any change in the MIL.
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Old 06-26-2012, 10:12 PM   #16
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The three plugs for the ECU go directly into the engine harness. The engine harness interfaces (IIRC) with the fuse block in the engine compartment which in turn connects with the dash harness that goes to the cluster so there is at least one more junction where things could be broken or unplugged. I only used the engine harness when I did my swap so I didn't pay much attention to the dash wiring. All that gear is NA6 on my car. Sorry I don't have better info...
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Old 06-27-2012, 12:01 AM   #17
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Are you sure? There are only two sides. The b/y goes back to a junction where its tied into the fuse box for "meter", but that is a bus that powers nearly all the lights in the cluster. I think this interfaces with the engine bay. The w/l one appears to go from the ecu 2r straight up to the cluster. I guess I'll find out because I'm going to trace that f0ker from end to end if I test it for ground and find out that the pin on the ecu is good.
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Old 06-27-2012, 12:12 AM   #18
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Not 100% certain but IIRC, most of those wires go directly to things like sensors and injectors. The parts that go off to interface with other parts of the car like the dash go through a plug/harness. In other words, the 3 plugs that go directly into the ECU and all of their wires can be unplugged and removed from the car without unplugging the back of the instrument cluster so there is a connection to check somewhere.
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Old 06-27-2012, 12:33 PM   #19
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oh look. electrical tape behind the gauge face.

f you dolphin and whale and south carolina for your hillbilly inspections!


problem resolved.
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Old 06-27-2012, 12:40 PM   #20
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Glad to hear!
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