Electrical problems

[mbpoindexter]

alright so I said F it and said lets see if this thing fires.

Cranked and fired right away like it should.

Gauges did some weird thing where tachometer and speedometer went up to 3 and 70 MPH, came down. Then PRND12 tranmission position all lit up flashing.

I shut it down and fired it again. All gauges working. 3 codes P0107 P0073 and P1652 as I expected.

I tried to clear the codes with my bypass wires set up for the P0107 and P0073 codes. None of the codes cleared, so I guess my bypass doesn't work.

I'm about to part this thing out. New motor new injectors can't even drive the mofo to the store. What a joke.

 

[mbpoindexter]

OK,

I removed the ECM connector harness at C2 to verify with my bypasses that I have low resistance to pins 3 and 35 where the sensor should be sending info. I have exactly what I expect. Plugged Harness back in. Read codes with only key on and got same 3 codes.

Went and unplugged one tap from sensor and re read codes and P1652 was erased. Gauges working.

Then went and plugged both bypasses in, turned ignition on. P0073 and P0107. Cleared codes and scanner says NO codes.

However with key on, check engine light is on but there are no codes. Read 3 times.

Im afraid to start it up because if I stop here I have reached the goal Ive been trying to get to for about 1,000 hours since I bought this jelopi.

Please give me your 2 cents.

 

[mbpoindexter]

So I am now having this weird P1652 code intermittently come up. Where all my gauges die.

I can't read the code when it happens but some times it goes away and I can get scan in. Only code coming up is P1652.

I tested resistance from Neg battery to D25 its not less than 10 ohms. It says replace ECM. I don't think that's the right way to go about this. Anyone else experienced this code? and dead gauges?

C-codes are listed earlier in thread.

 

[mbpoindexter]

Now I'm getting no throttle response, and when the cluster is working and I can get a scan in I can see P2121.

P1652 also shows up eventually

This piece of trash is all over the place.

 

[sag2]

The J1850 bus is used for generic scan tool communication. If you had a DRBIII factory tool you would be able to read the codes as it uses different protocol. You still have a problem with the D25 circuit, either shorted or a module going bad taking the bus down. The only way to diagnose is to disconnect each module and if that does not correct it, the circuit is shorted. Since it appears to be intermittent it makes it harder to confirm you have identified the problem.
On the other two codes, you might as well cut the wires at the T-Taps and solder in a couple new wires between the ECM and sensor. It appears you have identified the problem there.

 

[sag2]

For the p2509 remove the large wire from the battery to the fuse box and make sure it is clean. I still think you are having intermittent connections because you have messed with the ECM connectors so much.

 

[mbpoindexter]

I don't have P2509 anymore. That code has not come back at all. I think that was bad grounds or bad battery connections.

 

[mbpoindexter]

What do you mean disconnect each module? How do I do that? If I search for the D25 circuit in the FSM, its like everywhere.

How can I go about eliminating the modules? Because the problem is not intermittent right now, Its there to stay seems like.

 

[sag2]

You should have at least some of these modules that are on the BUS. Sentry Key, Hands Free, ECM, Radio, Amplifier, Transfer Case or Final Drive Control, Antilock Brake, Front Control. You have to access each module and disconnect the harness. If the problem still exists there is a short in the actual wire. The other diagnostic you can do is disconnect the batteries, then check the resistance from the D25 circuit at the DLC to ground. It should be less than 8,000 ohms. If it is considerably less than that (like 0-10 ohms) it is shorted to ground. You really need a scope to see the voltage, but a properly operating bus voltage should show between zero and seven volts when the bus is operating normally.
You can use the chart and Ohms Law to calculate the actual parallel circuit resistance you should see with the number of modules you have on your truck.

 

[mbpoindexter]

You should have at least some of these modules that are on the BUS. Sentry Key, Hands Free, ECM, Radio, Amplifier, Transfer Case or Final Drive Control, Antilock Brake, Front Control. You have to access each module and disconnect the harness. If the problem still exists there is a short in the actual wire. The other diagnostic you can do is disconnect the batteries, then check the resistance from the D25 circuit at the DLC to ground. It should be less than 8,000 ohms. If it is considerably less than that (like 0-10 ohms) it is shorted to ground. You really need a scope to see the voltage, but a properly operating bus voltage should show between zero and seven volts when the bus is operating normally.
You can use the chart and Ohms Law to calculate the actual parallel circuit resistance you should see with the number of modules you have on your truck.

Sag2,

Thanks for the help you've given so far. I need to read this a few times to understand and to find those modules you reference.

 

[mbpoindexter]

You should have at least some of these modules that are on the BUS. Sentry Key, Hands Free, ECM, Radio, Amplifier, Transfer Case or Final Drive Control, Antilock Brake, Front Control. You have to access each module and disconnect the harness. If the problem still exists there is a short in the actual wire. The other diagnostic you can do is disconnect the batteries, then check the resistance from the D25 circuit at the DLC to ground. It should be less than 8,000 ohms. If it is considerably less than that (like 0-10 ohms) it is shorted to ground. You really need a scope to see the voltage, but a properly operating bus voltage should show between zero and seven volts when the bus is operating normally.
You can use the chart and Ohms Law to calculate the actual parallel circuit resistance you should see with the number of modules you have on your truck.

Just a quick question, what are the chances I have a problem with the ECM itself? I assume pretty close to 0%.

 

[mbpoindexter]

You should have at least some of these modules that are on the BUS. Sentry Key, Hands Free, ECM, Radio, Amplifier, Transfer Case or Final Drive Control, Antilock Brake, Front Control. You have to access each module and disconnect the harness. If the problem still exists there is a short in the actual wire. The other diagnostic you can do is disconnect the batteries, then check the resistance from the D25 circuit at the DLC to ground. It should be less than 8,000 ohms. If it is considerably less than that (like 0-10 ohms) it is shorted to ground. You really need a scope to see the voltage, but a properly operating bus voltage should show between zero and seven volts when the bus is operating normally.
You can use the chart and Ohms Law to calculate the actual parallel circuit resistance you should see with the number of modules you have on your truck.

OBDII port D25 circuit port to ground resistance is 1,400 Ohms. Does that rule out the short to ground?

Just to verify I took off both positive battery terminals and checked the port to ground. 1,400 ohms.

The cluster is still dead, I have taken out radio, driver and passenger door lock/windows, and the lights on off switch. I'm firing the truck every time to make sure problem is still there. If it persists I am leaving those modules off.

Let me know if im doing this wrong.

Thanks Sag2

 

[mbpoindexter]

Ok, I pulled several modules and it did not seem like it fixed the problem. But, the BUS seems to be working now, however I think it was lucky, not from my efforts.

Also, throttle still dead. When I scanned I got P2121 related to the throttle and another about battery temperature sensor high. That may have been a result of my unplugging modules, I don't know.

I guess I have to wait for the BUS to act up again and start unplugging modules. I still don't know why my throttle keeps going dead and staying dead.

 

[Tuesdak]

On the other two codes, you might as well cut the wires at the T-Taps and solder in a couple new wires between the ECM and sensor. It appears you have identified the problem there.

I am curious if this was done. It wasn't said, but, if these wires being replaced were shorted and still hooked up: they are still a problem. This wouldn't be the first time and isn't going to be the last time part of a harness got smashed during engine removal or replacement.

@mbpoindexter It's problems like this that should make it clear that Electric Vehicles are not the way of the future. Hang in there as electronics IS the most difficult part of a vehicle to fix.

 

[MichaelOverfield]

@mbpoindexter It's problems like this that should make it clear that Electric Vehicles are not the way of the future. Hang in there as electronics IS the most difficult part of a vehicle to fix.

Well said, my saga on my 2009 has had be replace many modules and still not fix for it's stopping network communication betweent the scan tool and the ECU.. also NO DTCs. I have now replaced the harness between the body and ECU, but due to the complexity of just getting to that harness I lumped that work in with several other as yet not complete maintenance and upgrades.. that will take a while to complete to see if the harness did the trick, but I'm not too optimistic, there was not apparant damage of any kind to the original harness.

All this electronic crap is great when it works, but it's a nightmare to troubleshoot and fix.. makes me want to finish up my 1692 Land Rover, that basically has no electronics whatsoever, and only has a grand total of TWO fuses for the entire vehicle! That is sounding better and better all the time with stories like this one and others!

 

[mbpoindexter]

I am curious if this was done. It wasn't said, but, if these wires being replaced were shorted and still hooked up: they are still a problem. This wouldn't be the first time and isn't going to be the last time part of a harness got smashed during engine removal or replacement.

@mbpoindexter It's problems like this that should make it clear that Electric Vehicles are not the way of the future. Hang in there as electronics IS the most difficult part of a vehicle to fix.

Tuesdak,

Good point. I will do that in the morning.

I think I'm going to try and reset the APPS and mess with the truck tomorrow to see if I can get the BUS problem again to start eliminating the modules.

Hopefully as soon as I disconnect one of those modules with D25 circuit and check gauges they kick on. I would expect if that happens I can find the problematic wiring.

Thanks all for advice/assistance so far.

 

[sag2]

Just a quick question, what are the chances I have a problem with the ECM itself? I assume pretty close to 0%.

Probably not likely.

 

[sag2]

OBDII port D25 circuit port to ground resistance is 1,400 Ohms. Does that rule out the short to ground?

Just to verify I took off both positive battery terminals and checked the port to ground. 1,400 ohms.

That sounds correct. You need to determine what modules you do have and from the list I posted you can calculate approximate resistance.

The cluster is still dead, I have taken out radio, driver and passenger door lock/windows, and the lights on off switch. I'm firing the truck every time to make sure problem is still there. If it persists I am leaving those modules off.

Let me know if im doing this wrong.

Thanks Sag2

 

[sag2]

Since I do not know what modules you actually have I just picked what I thought were logical for an average truck and calculate 909 ohms. The more modules you have the lower the resistance, the fewer modules the greater the resistance.
Here is what I used.
1/3,300+1/10,800+1/10,800+1/10,800+1/10,800+1/3,300+1/10,800+1/10,800. That gives .0011

Then 1/.0011= 909 Ohms

Your truck will be different. In the above example if we have one less module with 10,800 ohms the total resistance would be 952 ohms.

 

[GCroyle]

Hard to follow all of this but that's a lot of help being administered by members on an electrical dioagnosis.

Nice job to the contributors and good luck to the OP.