Electronic engine control wizard, please help!!
I am having a hard time figure out what's wrong with my 1999 Dodge Ram (with
quad cab, short bed) 1500 4x4 with a 5.2L (318) engine and automatic tranny.
My truck would not restart after shutting it off when hot. It cranks but
engine doesnt start. It used to take about 30 minutes of cool down before it
would run again and now it would take an hour! I already figured out that
the PCM is not switching ignition coil circuit on and off causing no spark
out of the coil. Crank and cam sensor tested ok using a multimeter. Guages
and tach would not move when it wouldnt start (gas and volt guage stays in
same postion as when off without moving to correct reading when key is
turned on, tach doesnt move at all as normally does while cranking).
Sometimes speedometer says "no bus" when key is first turned on. After cool
down peroid, guages finally will show correcting readings,and it will
Just right before trying to fix above no start condition, the tranny was
acting up. Sometimes it would be stuck in 1st gear for all day or in limp
mode for all day. It had following codes P1757, P1763 and P1762. After
some diagnose work, it looked like a PCM is bad after trying new tranny gov
press sensor and solonid along with new tranny filter and fluid. Above no
start condition started shortly after replacing the PCM. The tranny still
Now, it is acting worst. It is running super rich and idles up and down
cold or hot. Current codes is as following PO122, PO117, PO107, PO112,
P1296 and P1764. All codes are similar: signal voltage too low. Following
flow charts carefully, PCM is assumed to be defective.
I back probed PCM connectors and input singal from all above sensors for the
codes are operating correctly. Yet, my scanner tool shows incorrect reading
While I wait for your help, I will try cleaning PCM ground system, do more
wire wiggle test, and even maybe put in old PCM back in and see if codes are
same. Seems like sensor voltages which shows incorrect readings on scanner
tool change when I bang on the truck espically interior driver area. Wires
under steering colum looked ok. Please help!