How to find and repair short circuit?

[Ardy]

I’ve had a crankcase pressure sensor DTC which I posted about earlier and no one could help. I’ve now done some diagnosing using the shop manual and I’ve found the problem. But now I have no idea how to fix it. Any help would be appreciated.

Following the HG Pinpoint test in the shop manual, I got to this box.

Now it says “repair the short circuit”
Totally lost…

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[IPOGT]

I’ve had a crankcase pressure sensor DTC which I posted about earlier and no one could help. I’ve now done some diagnosing using the shop manual and I’ve found the problem. But now I have no idea how to fix it. Any help would be appreciated.

Following the HG Pinpoint test in the shop manual, I got to this box.

Now it says “repair the short circuit”
Totally lost…

I'd start by tracing back the 5.6V to each junction point along the cable feeding the circuit and look for a physical cause of a shorted wire via pinched, melted, pieced or pierced. Look for shorts in fusebox etc. The flow chart is specifically TELLING YOU there IS a short. You just need to find it. 500k is all I needed to know. Be persistent.

 

[JCN]

I see what the chart is saying but don't follow, hg4 is looking for 3.6-4.3 with normal load (sensor connected). hg7 is showing a slight reading to ground on pin1, 0 ohms would be a dead short. hg8 is pin 1 volts no load at 5.6, not knowing for sure what that should be but it's higher thanhg4, which it should be with out the load on it. is there any test for the sensor, I'm not seeing their "short"

 

[JCN]

read it again and with the hg4 actual volts a little low and unstable it feels more like a damaged wire or poor connection which leads back to what ipogt says about following wires inspecting connections ect. you may have to resort to ohming each portion of wire while someone wiggles things looking for fluctuation on meter. it could be broke internally and not visible. hope for your sake it's obvious damage you can see or feel!

 

[Ardy]

Thanks for the replies. I’ve visually inspected the wires from the sensor all the way to the ECU and found nothing. Anything else I could do?

 

[IPOGT]

Thanks for the replies. I’ve visually inspected the wires from the sensor all the way to the ECU and found nothing. Anything else I could do?

Move the harness while monitoring the DMM for fluctuation in Kohms.

 

[Cobra Jet]

Thanks for the replies. I’ve visually inspected the wires from the sensor all the way to the ECU and found nothing. Anything else I could do?

A visual of a wire harness outer casing does not always mean that the actual copper or metal wire inside of it is not damaged.

Also, check any connector along the route to make sure the pins inside of the connector are 1) making proper contact to its mated plug and 2) that the wire or wires have not become detached or loose from the pin.

 

[JCN]

A visual of a wire harness outer casing does not always mean that the actual copper or metal wire inside of it is not damaged.

Also, check any connector along the route to make sure the pins inside of the connector are 1) making proper contact to its mated plug and 2) that the wire or wires have not become detached or loose from the pin.

while you are checking connections a good idea would be to spray them with contact cleaner even if they look clean. When you're dealing with low voltage and milliamps it doesn't take much to disrupt a circuit and it can be a pain to find. {40 years of railroad signal system work} I will caution you even though most contact cleaner claims to be dielectric I would unhook the battery prior to and for 20 minutes or so if you use spray, don't want to set you up for other issues. Jim

 

[Ardy]

Thanks for the tips guys. Update: I disconnected the PCM side of the wiring harness and looked for the 5.6V on the PCM pins. No voltage so the short circuit isn’t inside the PCM, it’s in the monster wiring harness. Would buying a short circuit finder be useful here?

Car is under warranty just super paranoid about letting someone else work on my car. Last resort I’ll take it in.

 

[JCN]

Thanks for the tips guys. Update: I disconnected the PCM side of the wiring harness and looked for the 5.6V on the PCM pins. No voltage so the short circuit isn’t inside the PCM, it’s in the monster wiring harness. Would buying a short circuit finder be useful here?

Car is under warranty just super paranoid about letting someone else work on my car. Last resort I’ll take it in.

I've only used a short finder a couple of times, from my limited experience they are most effective with a hard short. 0 ohms would be a hard short, 5ook is very little. Still feels like an open wire or high resistance in a connection to me?

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