Trucks been throwing the 1689 code. I started to test the truck to see how often it throws the cel. 1689 every time.

It will cut the power for a few seconds EVERY time it hits 2500ish rpms, it only happens at 2500rpm's. why would it be doing it at a specific rpm? I thought for a while it was only doing it under hard acceleration but its cutting out at 2500??????

Any ideas???

Hi, Ben. What is the vehicle description? Any mods, programmer, etc?

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[h=1]http://articles.mopar1973man.com/2nd-generation-24v-dodge-cummins/59-obdii-error-codes/228-p1689-no-communication-between-ecm-and-vp44

DTC P1689: NO COMMUNICATION BETWEEN ECM & INJECTION PUMP MODULE (OBDII)[/h] [h=2]Monitor & Set Conditions[/h] Communication between Engine Control Module (ECM) and fuel injection pump module is monitored when ignition is on. Injection pump module is referred to as Fuel Pump Control Module (FPCM) in test procedures. DTC may be stored if the time between CAN messages is more than 3 seconds or FPCM does not receive CAN message.

[h=2]Possible Causes[/h]

[*] Wiring & Connectors

[*] Fuel Injection Pump Relay Output Circuit Open

[*] Ground Circuit Open Or High Resistance

[*] Datalink (+) Circuit Open

[*] Datalink (+) Circuit Shorted To Ground

[*] Datalink (-) Open

[*] Datalink (-) Shorted To Ground

[*] ECM

[h=2]Testing[/h] 1. Turn ignition on with engine off. Using DRBIII® scan tool, check for DTCs. If Good Trip Counter for DTC P1689 is displayed and not equal to zero, go to next step. If Good Trip Counter for DTC P1689 is displayed and equal to zero, go to step 3 .

2. 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 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.

3. Ensure ignition is 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. Turn ignition on with engine off. Using DVOM, measure voltage between ground and terminal No. 7 (Red/Light Green wire) on FPCM harness connector. If voltage is 8 volts or greater, go to next step. If voltage is less than 8 volts, perform DTC P0215: FUEL INJECTION PUMP CONTROL CIRCUIT test.

4. Turn ignition off. Ensure FPCM connector is still disconnected. Disconnect ECM harness connector. Check for poor connection/terminal contact at ECM harness connector. Repair as necessary. Connect a test light between battery voltage and terminal No. 6 (Black/Tan wire) on FPCM connector. This is the ground circuit for FPCM. If test light illuminates brightly, go to next step. If test light does not illuminate brightly, repair open or high resistance on Black/Tan wire between FPCM and ground connection. Ground connection is located at ground connection for negative battery terminal.

5. Ensure ignition is off and FPCM harness connector and ECM harness connector are still disconnected. Using DVOM, measure resistance of White wire between terminal No. 2 on FPCM harness connector and terminal No. 13 on ECM harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or greater, repair open or high resistance in White wire between FPCM and ECM.

6. Ensure ignition is off and FPCM harness connector and ECM harness connector are still disconnected. Using DVOM, measure resistance between ground and terminal No. 2 (White wire) on FPCM connector. If resistance is 5 ohms or greater, go to next step. If resistance is less than 5 ohms, repair short to ground in White wire between FPCM and ECM.

7. Ensure ignition is off and FPCM harness connector and ECM harness connector are still disconnected. Using DVOM, measure resistance of Black wire between terminal No. 1 on FPCM harness connector and terminal No. 23 on ECM harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or greater, repair open or high resistance in Black wire between FPCM and ECM.

8. Ensure ignition is off and FPCM harness connector and ECM harness connector are still disconnected. Using DVOM, measure resistance between ground and terminal No. 1 (Black 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 Black wire between FPCM and ECM.

Sorry should have been more specific, its a 2001, no programmer, All stock besides a 4 inch exhaust. I just bought the truck, It has a new vp44 as well as a new stock replacement lift pump. I just bought a fuel pressure gauge and have not hooked it up yet, so i have no clue about fuel pressure. cant really check the pressure anyways because the truck shuts down at 2500 rpms.

P1689 code is a communication problem or wiring problem typically... But I would still get that gauge hooked up and installed so you can verify it not a fuel issue causing excess heat damage.

Any idea why it would be specific to 2500rpm's? i could see it being intermittent but its specific to 2500rpm's no matter how much throttle im giving it.

Vibration? Loose wire connector?

I dunno i have checked every wire i could find to see if its loose. im at a lose here.I did however Test the truck some more and it will also throw the code while revving the engine in neutral, so its not specific to driving under a load, it will throw the code everytime it hits 2500rpms, under load or in neutral.

Well the trucks at the shop now, ill let you guys know what they find out.

Mechanic says they tested everything and the Ecu is shot, So i bought a new Ecu, and they will be programming it and installing it tomorrow, we shall see if this was the problem........