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Cautions always apply. Plus, other people read these forum posts and apply the advice given to their own situation. No harm in providing as much information as possible.
Yes, that’s a good point.
It says nothing about the rate of pulse, but that’s not really what I’m concerned with yet. Even without cranking, I think if the ignition is on, I should get a constant 12V from the ECM.
Thinking about it more, the reason no one has come up with my test yet might be that it doesn’t really tell you anything unless you don’t know what’s going on. My suspicion is that if Eric didn’t have a ground before cranking, he would know that something is wrong coming from the computer. The ignitor failure that he shows starts with a ground, then cuts out completely when cranking. I would guess that when these fail, they can still provide a constant ground but just can’t handle the pulsing. My test would show that the ignitor is still capable of providing at least a constant ground, and that if it’s not doing that with the ignition on, then the ECM isn’t sending a signal. The ignitor might still be bad, but I won’t know until I work out the ECM problem.
I’m really leaning toward finding a used cheap computer. I think the ECM bases the pulse from the TopDeadCenter/CrankshaftPosition/CylinderPosition sensors, and in principle those could go bad, but I don’t know that they would cause a problem with the constant ground before cranking. That and the check engine light issue.
Depending on how the electronics for the igniter were designed, applying 12v directly may not do what you think. In digitally controlled circuits, many are edge based. Meaning, the 12v being applied may not itself be the trigger, but rather 12v being applied and then removed in a prescribed period of time. A pulse of a certain width. Example, 12v being applied for 10ms and then removed. It is the falling edge that is the actual trigger, not just 12v being applied. Additionally, circuits can use the rising edge instead of the falling edge.
Also note that many digital circuits use 5v signal/feedback lines, and applying 12v to these parts of the circuit can instantly damage them, frying a formerly good (and potentially expensive) component.
Note taken, but does any of this apply in this situation? The direct quote from the manual about the signal from the ECM to the ICM is
“Note: Standard battery voltage is 12V
…
With ignition switch ON (II): battery voltage
With engine running: pulses”Is your Honda equipped with an immobilizer feature?
Hadn’t thought of that, but I don’t think so. I’ve read a ton of diy guides about this car, and I don’t remember an immobilizer ever being mentioned. A little searching didn’t turn up any confirmed 1st generation CR-Vs with immobilizers, and a couple people saying they were not equipped at all, so I’m going to strongly guess no. Thanks, though.
Thanks for the reply.
Do a ‘confidence test’ on the coil.
I should have mentioned, I did do this, as per page 4-20 in the FSM. The specs in there are 0.63-0.77 ohms for the primary (I got 0.8 ohms, but I’m not willing to deem that a problem until I get the ICM working) and 12.8-19.2 kohms for the secondary. I can’t remember what I had for that, but it was well inside the range.
Ok, so you have done the ‘confidence test’ on the coil, now you need to check if the coil is being switched on and off. Disconnect the wire at the – side of the coil primary. A continuity tester or ohmmeter can be used for this. Connect one side of the tester to a known good ground, and the other side of the tester to the disconnected wire. Now, you or a helper, crank the engine. The tester should show the continuity to ground being switched on and off as the engine turns. If it does, your igniter is good. If the tester stays off or is lit constantly, the igniter is bad.
This is equivalent to the test done in the video, except Eric uses the car battery as the power for his continuity tester. I can do this test, and the tester stays off, but my problem is that the tester was off to begin with. In other words, I think that the test has an unspoken first rule of “the ignitor should provide ground to the coil continually when the key is ON and engine stopped, and switch on and off when the engine cranks.” I get no continuity ever, which leads me to believe this test is not appropriate (yet).
As I’m looking through the manual, I think I can devise a test of the ICM that I’m surprised I haven’t seen online yet. Page 11-72 (terminal 13) shows that the ECM sends 12V to the ICM when the ignition is ON, and pulses when engine is running. So if I manually provide 12V to the ICM, and it does ground the coil, than I have confirmed that the ICM is not getting a signal from the ECM, correct? Granted, this doesn’t completely test the ICM, but at least part of it.
Oh, yeah, almost forgot, I have no check engine light when I start the car. It’s supposed to go on for two seconds then off, and the ECM/PCM troubleshooting starts with this symptom. So I feel pretty sure that the computer is the problem, but I’d like a little encouragement before I put any more parts in it.