Can someone answer some questions about this article concerning measuring AC noise across the fuel fuelpump. My question is what position do i need to have the key when i probe terminals 48 and 50 on the ECM harness. The article isnt clear on that. [TABLE=class: tborder, align: center]

[TR]

[TD=class: thead, align: right] #2 (permalink) [/TD]

[/TR]

[TR]

[TD=class: alt2, width: 175]TexasTurbo

Diesel Head

Join Date: Aug 2011

Location: Cut N Shoot, Texas

Posts: 1,555

Thanks: 157

Thanked 346 Times in 274 Posts

iTrader Score: 2 reviews, 100%

TexasTurbo's Truck Pics

[/TD]

[TD=class: alt1]Mopar1973Man's Dodge Cummins Articles - P1690 VP44 CKP Sensor Does Not Agree With ECM CKP Sensor

[/TD]

[/TR]

[/TABLE]

[h=2]Monitor & Set Conditions[/h] Fuel Injection Pump Crankshaft Position (CKP) circuit is monitored when ignition is on and engine is running. DTC may be stored when no signal exists within specified window parameters with no Camshaft Position (CMP) sensor or CKP DTCs present.

[h=2]Possible Causes[/h]

[*] AC Noise Across Fuel Transfer Pump

[*] Other DTCs Present

[*] Wiring & Connectors

[*] Fuel Injection Pump Static Timing

[*] Fuel Sync Signal Circuit Open

[*] Fuel Sync Signal Circuit Short To Ground

[*] ECM

[h=2]Testing[/h] 1. Measure AC noise to ECM by connecting DVOM between ground and terminals No. 48 and 50 (Red/White wires) at ECM harness connector. If AC voltage is 25 mV rms or less, go to next step. If AC voltage is greater than 25 mV rms, replace fuel transfer pump. See appropriate REMOVAL, OVERHAUL & INSTALLATION article.

2. Turn ignition on with engine off. Using DRBIII® scan tool, check for DTCs. If no additional DTCs exist, go to next step. If any additional DTCs exist, repair other DTCs first. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .

3. Using scan tool, check Good Trip Counter for DTC P1690. If Good Trip Counter for DTC P1690 is displayed and equal to zero, go to next step. If Good Trip Counter for DTC P1690 is displayed and not equal to zero, go to step 5 .

4. Turn ignition off. Disconnect FPCM harness connector. FPCM harness connector is located on end of fuel injection pump. Check for poor connection/terminal contact at FPCM harness connector. Repair as necessary. Disconnect ECM harness connector. ECM is located on driver's side of engine, just in front of fuel transfer pump and contains a 50-pin connector. Check for poor connection/terminal contact at ECM harness connector. Repair as necessary. Using DVOM, measure resistance of Dark Green wire between terminal No. 8 on FPCM harness connector and terminal No. 18 on ECM harness connector. If resistance is less than 5 ohms, go to step 7 . If resistance is 5 ohms or greater, repair open in Dark Green wire

between FPCM and ECM.

5. Turn ignition off. At this time, conditions required for DTC to be stored are not present. Inspect wiring and connectors between FPCM and ECM. FPCM is located on top of fuel injection pump. ECM is located on driver's side of engine, just in front of fuel transfer pump and contains a 50-pin connector. If no problems exist, go to next step. If any problems exist, repair wiring or connectors as necessary.

6. Check fuel injection pump timing. See CHECKING FUEL INJECTION PUMP TIMING under FUEL INJECTION PUMP TIMING in ON-VEHICLE ADJUSTMENTS - RAM PICKUP - DIESEL article. If fuel injection pump timing is okay, go to next step. If fuel injection pump timing requires adjustment,

adjust fuel injection pump timing as necessary.

7. Ensure ignition is off. Disconnect FPCM harness connector. FPCM harness connector is located on end of fuel injection pump. Disconnect ECM harness connector. ECM is located on driver's side of engine, just in front of fuel transfer pump and contains a 50-pin connector. Using DVOM, measure resistance between ground and terminal No. 8 (Dark Green wire) on FPCM harness connector. If resistance is 5 ohms or greater, replace and program ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. If resistance is less than 5 ohms, repair short to ground in Dark Green wire between FPCM and ECM.

That is interesting about the AC noise they claim is from the lift pump. The only reason I could see that is a internal motor/brush issues that might generate a small amount a arcing or AC like noise. But typically the AC generated noise would be the alternator. If you already using a AirDog, Raptor, or FASS this is a mute point.

Then checking the key on the bosch Vp44 injection pump shaft for damage or the wrong one.

Beyond that the rest of it checks the typical stuff wiring from pin to pin from the VP44 and the ECM. Looking for weak connections (greater than 5 ohm) or shorts to ground.