Engine Performance problem
2003 Dodge Ram V8 Two Wheel Drive Automatic
5.9 engine, JTEC pcm. No start. +5volts ref output from pcm is only 2 volts and decreases to ~1.7 v while cranking. + The fuel pump doesnt energize and the auto shutdown relay doesnt energize either when key is rotated to RUN before START.
Ok so tell me have you checked fuse number 2 and number 17 and 19? These all in some way tie into the fuel pump and shut down relay. If these are good then I need you to check the light green wire with the black stripe going to the fuel pump relay and let me know if you have power there with key on engine off. Get back to me with what you find.
June, 26, 2009 AT 8:37 PM
Fuse #2 to the ASD relay is OK. Fuse #17 to the Fuel Pump Relay conntact (30) is oK. Fuse #19 supplying +12V to the PCM, C1-22 is OK. The LG/BK wire going to the Fuel Pump Relay is providing the +12V to the Relay Coil. I cut the BR Relay Coil wire going to the PCM & clipped it to Ground. The Pump ran & produced 50+ PSI. The PCM wasn't pulling this BR to Ground during crnking. The relays are both good. I swapped them & can still get the Pup to run when grounding the snipped BR wire.
June, 27, 2009 AT 8:45 AM
You need to fix the br wire it must have a short in it. It is suppose to go to the computer the power train module pin number 19. SO check continuity from one point to the other and fix that problem and the pump should work as it is suppose to unless the computer isn't sending the signal then you have a bad computer.
June, 27, 2009 AT 10:02 AM
Do you have any thoughts on the +5 V PCM supply (C1-17) output being only +2V?
July, 1, 2009 AT 8:46 AM
PCM supply voltage to what? Where is C1-17? My references don't show that.
July, 1, 2009 AT 10:33 AM
C1-17 is a 5 Volt Refernce that the PCM outputs to several sensors; Cam sensor, Crank sensor, MAP, to name 3. I think it powers more sensors such as TPS.
July, 2, 2009 AT 9:03 AM
Ok so tell me do you have any trouble codes set? Is the battery at a full 12 volts. Are you getting power to the auto shut down relay and power out of it? Let me know what you find.
July, 2, 2009 AT 10:07 AM
I periodically charge the battery to full capacity. The ASD is not being energized (pulled to ground) by the PCM. The ASD relay (and the Fuel Pump relay) are both OK as I indicated in a previous post. I cant get the PCM to issue any trouble codes except an ERR message that shows up on the OBD II reader.
July, 3, 2009 AT 9:16 AM
So do you have power to the auto shut down relay? Have you checked fuse number 2 (30amp) in the under hood fuse box? The computer does not pull the auto shut down relay to ground the ignition powers it up it grounds through the chassi according to the wiring diagram I am looking at. It sends power to a number of points. I also need you to check fuse number 28. What else on the truck don't work?
Looking at the engine performance wiring diagram I need you to check fuse 17 (15amp) and fuse 49 (20amp) these power the fuel pump and auto shut down too. I also would like to know if the light green wire with the black stripe at the fuel pump relay gets power with the key on. Do you have spark? Check ptc 1 (7.5amp fuse) in the under hood fuse relay box. I also would like to know if the dark blue wire with the yellow stripe at the auto shut down relay has power with key on, and then the brown wire at the fuel pump relay does it get power with key on? Let me know what you find and we will go from there.
July, 5, 2009 AT 10:21 AM
Yes & Yes for 1st 2 qyuestions. I indicated this in a previous post. The ASD relay coil (terminal 85) gets +12V thru fuse #2. The other side of the coil (terminal 86) goes to the PCM C3-3 (auto shutdown relay control), not chassis ground. I tracked the DB/YL wire & verified this.
All fuses are good. They have been checked at least twice each.
As far as what else doesn't work, evrything else checked works such as lights, radio, signals, etc.
Fuse 17 & 49 are good. The LG/BK wire has power with the key ON.