I think my ECM is toast. How do I confirm?

[hemi@]

Straight to the point. I hooked up some batteries and pull my truck out to spin it around a month or so again. I think I may have fried the ECM by forgetting to unhook the batteries and resuming welding on the truck. the truck is apart and 100 other things are unplugged So id like to confirm it is the the ECM or maybe TIPM?
The truck:
It’s a 04.5 and turn signals do not have relays but are computer controlled. Some 03/04 have relays I understand. ECM is 2 plug
The symptoms: powers up good. Turns over quick. No attempt to start. Then gauge cluster comes on and seems to work. Smarty scanner does not recognize the truck... just asks for key off>key on>key off> key on. It doesn’t not say no stored codes.

the real strange thing that I’m looking for any insight on.. the lift pump cycles on and off when the key is on. Not like the 30 prime but more like a horn sounding on a car alarm. Steady on/off.

Any insight would be appreciated. I don’t have a big scanner just the smarty, I can tell the sensors are getting 5v and not 12 so I’m optimistic that maybe the ecm isn’t toast?

 

[sag2]

I'm a little confused. Did it start and run before you started welding on it? Welding on a truck with batteries connected is usually not a problem if the grounds are good. If they are not, the welder will try and find a ground anywhere it can.

 

[Ozymandias]

Disconnect the batterys first, this will reboot the system. That's is the point to start troubleshooting.

 

[cerberusiam]

Smarty is likely not seeing the ECM because the harness is unplugged. You really cannot tell much if you have too many things unplugged as it will need signals forma lot of places to actually start. The fact the it cranks and the cluster comes on and looks right is good news. Reconnect all your harness and sensors then test again.

 

[hemi@]

I'm a little confused. Did it start and run before you started welding on it? Welding on a truck with batteries connected is usually not a problem if the grounds are good. If they are not, the welder will try and find a ground anywhere it can.

It’s confusing so I didn’t want to get into a lot of detail but I’m in the process of doing a roll cage, relocating the batteries and many other things. It wasn’t uncommon to hook up the extended battery cables to the a battery that was on the floor so I could start the truck and move it out of the garage. That being said.. the battery relocation is complete, truck had been running and all I had been doing was cage work. I’m fairly sure it was the welding that killed the ecm because I know for a fact I have put the mig gun to the truck without the ground clamp being attached because I vividly remember the frustration of trying to roll a creeper around under the truck with all the extension cores, corded drop light, grinders, and grounding clamp all getting in the way. I was just looking for positive identification of failed ECM or TIPM.

 

[hemi@]

Smarty is likely not seeing the ECM because the harness is unplugged. You really cannot tell much if you have too many things unplugged as it will need signals forma lot of places to actually start. The fact the it cranks and the cluster comes on and looks right is good news. Reconnect all your harness and sensors then test again.

When I said o said many things are unplugged I meant things more along the lines of interior stuff, doors headlights. I went through everything under the dash a while back and got rid of the alarm system and turbo timer and other added complication, and because very familiar with the harness down there. They are all plugged in. I only mentioned things being unplugged because I know CAN systems can get funny with that stuff.

 

[cerberusiam]

Well, engine cranks so it isn't the FCM, an 04.5 has an FCM and PDC not a TIPM. The fact that Smarty won't connect means the OBD link to the data bus is down. If the cluster gauges seem to work for fuel, battery, etc, that part of the data bus is up. Have you run a cluster test to errors in the odometer window? Have you run the key trick to see what errors show in the odometer window?

Since it is an 04.5 it isn't CAN bus but it can be picky about what sensors are hooked up and what may be shorted like the fan. Start unplugging peripherals like the fan and double check the OBD port to make sure a wire is not off there.

 

[hemi@]

Well, engine cranks so it isn't the FCM, an 04.5 has an FCM and PDC not a TIPM. The fact that Smarty won't connect means the OBD link to the data bus is down. If the cluster gauges seem to work for fuel, battery, etc, that part of the data bus is up. Have you run a cluster test to errors in the odometer window? Have you run the key trick to see what errors show in the odometer window?

Since it is an 04.5 it isn't CAN bus but it can be picky about what sensors are hooked up and what may be shorted like the fan. Start unplugging peripherals like the fan and double check the OBD port to make sure a wire is not off there.

Thank you, that’s Good info and something I can look into. I'm not familiar with the key trick or the cluster test so I’ll learn about that and get back to you with the results.
The instrument panel lights up the warning indicators, turn signals function normal, and it does that test move thing on the gauge needles, but upon closer inspection I realized that it reads empty fuel. Its been a while but I’m fairly sure I left it completly full.
Does this odd cycling on/off of the lift pump indicate anything? I really thought someone would have SOME kind of experience with that... it looks like the ECU directly signals the relay for the FASS pump.

 

[hemi@]

Well, engine cranks so it isn't the FCM, an 04.5 has an FCM and PDC not a TIPM. The fact that Smarty won't connect means the OBD link to the data bus is down. If the cluster gauges seem to work for fuel, battery, etc, that part of the data bus is up. Have you run a cluster test to errors in the odometer window? Have you run the key trick to see what errors show in the odometer window?

Since it is an 04.5 it isn't CAN bus but it can be picky about what sensors are hooked up and what may be shorted like the fan. Start unplugging peripherals like the fan and double check the OBD port to make sure a wire is not off there.

Fuel gauge doesn’t work, gear indicator doesnt work, 3 turn “key trick” produced no result. Maybe I did it wrong? But the cluster test revealed c- codes 67 01. 68 43 and then 00 00