ECM-6300 and ECM-6B00 2000 V70R [BAD Battery to fusebox supply cable!] EPIC Troubleshooting Topic is solved

[RickHaleParker]

Does anybody know if the signal from the ECU for the CEL is supposed to be power or ground? The diagrams aren't very clear.

What engine control unit are you looking at? It sounds like you are looking at MSA 15.8 which is the ECM for Diesel engines.

[bmdubya1198]

What engine control unit are you looking at? It sounds like you are looking at MSA 15.8 which is the ECM for Diesel engines.

I'm looking at ME7. The only difference on my diagram for MSA is that the ETS light wire goes to pin 49 instead of 41 on ME7.

[RickHaleParker]

I'm looking at ME7. The only difference on my diagram for MSA is that the ETS light wire goes to pin 49 instead of 41 on ME7.

CDM internal diagram is in group 38. Find the Fuse at A:18, ETM and CEL light. From there you can figure it out.

[bmdubya1198]

This fuse?

[RickHaleParker]

This fuse?

Yes

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[abscate]

I would look at that regulator in that circuit. That’s exactly whereafailure would cause flickering.

That filter circuit is another possibility. Probably filtering ac ripple on the alternator


Monitor voltages on each side

[bmdubya1198]

I wonder if those parts are easily replaceable. Ugh... this means I'll have to tear apart the dash and cluster. Not hard, but of course it's raining and my garage is occupied by a German.

Since both the CEL and ETS light are affected, I assume the issue is more likely on the power side (within the cluster). What's strange is that when I swapped in a spare cluster, the codes persisted. Granted, I couldn't test very much since the CDM is coded and part of the CAN bus, but IIRC, it didn't change anything.

The biggest question I have is WHY is the signal wire for the CEL (I'm assuming the ETS one would be doing the same when it's lit) grounding itself every second or so?

The voltage I'm seeing on the CEL wire to the ECU is perfect, should be near 0v if the CEL is illuminated. So that's not a concern.

[bmdubya1198]

Did a little more troubleshooting today. I checked the values against the specs in VIDA for the signal ground, 30-supply, power ground, and 15-supply. Everything was perfect. I checked the voltage on the CEL wire. It should be around 1v or less with the CEL on, and battery voltage with it off. All good with the key on. While it's running, it begins the flickering, and the voltage jumps between 12v and a few mV. That's just the circuit's response to the flickering, makes sense to me.

Now my thinking with the test light keeping it steady is that it overloads the circuit trying to power on the test light, so that wire never goes up to 12v. This keep the CEL from turning off, since the circuit should have 12v with the light of and minimal voltage with it illuminated.

The only common circuit between the ETS light and the CEL is the circuit on pin A18 of the cluster (as Rick pointed out), which includes the fuse, filter, and 8v regulator. Although the cluster seems to be getting ample input voltage, I feel like the problem lies within one of those components in the cluster. That makes the most sense. Since the wire for the ETS light is showing 12v and it's off, I don't think there's a problem on the control side (being the ECU).

Anyone think I'm on the right track here? Trying to put this sort of stuff together really makes my head spin... I'll have it all figured out in my head, then try to write it down or make sense of it, then I'll remember another details that invalidates my hypothesis. That said, I'm feeling fairly confident with this one.

[RickHaleParker]

Since both the CEL and ETS light are affected, I assume the issue is more likely on the power side (within the cluster). What's strange is that when I swapped in a spare cluster, the codes persisted.

The marked yellow line is a common power bus (+). You turn on something on the power bus by grounding the other side of the component. I think you have a short to ground in the harness between the CDM and the ECM. The fact that swapping CDMs does not change anything is evidence that the problem is external of the CDM.

1. Power off.
2. Pull CDM.
3. Locate wires for ETM & CDL.
4. With a Ohm meter, check to see if ETM & CDL are shorted together.
5. With a Ohm meter, check to see if ETM & chassis ground are shorted together.
6. With a Ohm meter, check to see if CDL & chassis ground are shorted together.
7. 4,5 & 6 should show open circuit (∞) not shorted or Semiconductive.

You might need to wiggle wires to get a short to show its hand.
The test light maybe providing a steady ground (1) vs a intermittent one in the harness. That would explain flicker vs steady.

(1) The resistance of a test light is just slightly above the resistance of a piece of wire. Severe instrument loading enough to affect circuit behavior. Use something like a Multimeter with a high impedance to minimize instrument loading.

[bmdubya1198]

Correct, using the multimeter doesn't affect the flashing.

I don't think there's a short to ground on the harness. I checked this last year, and I'm almost certain that there's not an issue. I checked the resistance to ground on both of the wires and to each other, and the resistance on my cousin's '99 S70 was exactly the same as I'm seeing on my car. IIRC, I saw about 65 ohms to chassis ground on either wire.

What I don't understand is how a ground shorts to ground. If it was shorted to ground, shouldn't it be steady? Plus it's a pretty consistent pattern. That's the confusing part.