Beam52

Well I put the truck back together today and the rpm gauge works, the abs light went off then came back on, the air bag light went off. Still have no bus, cel, intermittent abs light.

Update: I have 2.43 and 2.45 volts to the pcm, they are the wrong voltage but it is voltage. I have -bus voltage to the ecm plug but no voltage to the +bus. I have .3 ohms from the ecm -bus to the pcm -bus and OL when the +bus wire is ohmed out. Also when I plug the pcm in the voltage is killed. I have the abs, air bag, radio unplugged. So I’m thinking I have a short in the harness somewhere. What do y’all think? Just tested the obd connector, at first it had 1.5 volts to both -&+ bus wires, the I unplugged the timing control module and it jumped to 2.43 and 2.45v. Shorter tcm?

I have discovered that I have no ground to the fuse box under the hood. I can put the leads on the positive post on the fuse panel and onto the negative terminal on the battery and get 12.5v but none testing the negative terminal

Would a bad sensor cause the bus to go down? I have codes p0113 p0122 p0237 and P1698 which says it is not found in the database. Also the first DTC1 is no communication with vehicle ecu

I’ve got the correct voltage at the pcm lol alternator is putting out 14 volts to both batteries, ac volts is it 0.025. I honestly am very stumped right now

Well I installed it thinking it was the fix and still have the no bus and no cluster. Also have a new used cluster and that wasn’t the fix either. I don’t believe it’s the ecm because the truck still runs and drives and has a voltage reading on the code scanner. I also have just over 1 year old batteries and a newer alternator.

Reman for $650 and 2 year warranty

Well got a new Pcm installed, still no bus. Back to the diagnosing.

Ok so I hooked up a friends scanner to it today. It reads it has 9.75 volts to the ECM, but has a DTC saying it has a communication error with the ECU. Bad PCM? Also have a P1698 code

Is it a give away that the PCM or ECM is good given that the truck runs and drives like normal?

I was wondering if something such as my bully dig tuner or like Alexio mentioned the intake grid relay would short it out causing the no bus, I’ll have to take the positive cable off and see what happens. Same with the tuner

All he did was hook up and gave me those three things from the Bosch scan tool lol so I’m gonna replace the temp sensor and maybe get a boost fooler, maybe clean the map sensor too. But definitely going to clean the cluster connections and if anything I’ll get one for $300 included exact mileage reset. But thanks for trying! At least someone tried.

Well went to O’Reillys and they pulled up high voltage to the coolant temp sensor, over-boosting and no DTC detected. I don’t believe any of these would cause a no bus would they?

Hey everyone! I have a 2002 Dodge CTD auto with 277k. I’m getting the “no bus” message on my odometer screen with codes 900 920 921 940 950 and 999 on the self check. The CEL, ABS, low fuel and air bag lights are on. I’ve cleaned up the connections at the PCM and fuse block, cleaned grounds and still no fix. The truck does start and drive normal so I don’t believe it’s the PCM. Any input is welcome thanks!

That's what I thought. And this is for HVAC and cruise correct?

Is this not a check valve that's in line? https://www.google.com/search?q=2001+dodge+ram+vacuum+check+valve&client=ms-android-verizon&biw=360&bih=512&tbm=isch&prmd=sivn&source=lnms&sa=X&ved=0ahUKEwiBz9qcwa7YAhVNzmMKHTYFB7oQ_AUIvgIoAg#imgrc=tWyJ9oiy8SBECM:

Hopefully I won't have to, tonight I didn't turn it to off most of the night shutting the truck off and on numerous occasions. The heat to the floor worked great. So I an thinking one of those vacuum pods, check valve or the control panel.

Hey everyone! Brand to this site. Hoping to get some answers. So my cab heater is acting up, it will blow warm to hot air through the defrost and face vents but will blow cooler air through the floor or any mix setting. Sometimes I will hear a thud or something dropping on the passenger side dash. I have a new radiator, thermostat, water pump, blend door actuator coupler (heater treater). I'm wondering if this is a vacuum or door problem, maybe even a heater core problem. Also on defrost from the driver vent to the passenger its got great air flow to almost none, so thats also a concern. Thanks!