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2nd Gen Guru
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2,641 Posts
Discussion Starter #1
Well gang...

Mopar1973Man is back out in his shop and found the cause of P1689 error codes.

P1689 - No Communication Between ECM and Injection Pump Module Data link circuit failure between ECM and fuel injection pump. Low power, engine derated, or engine stops.
A lot of us assume its the injection pump that causes this which in most cases could be. But I was doing a fuel pressure test (cranking). This requires to pull the fuel system relay out of the PDC box under the hood...




Lower left side labeled fuel pump...

When this relay is missing the VP44 doesn't energize nor pump fuel. It allows you to do the cranking test. But it also sets a P1689 and CEL light. So for all of you that have a P1689 error code present check your fuel pump relay first by trading with another relay!
 

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2nd Gen Guru
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2,641 Posts
Discussion Starter #3
That's odd 52 people look at the thread and no comment...:eek:
 

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Heavy Equip. Is My Life
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65 Posts
That's odd 52 people look at the thread and no comment...:eek:
I am in awe... still trying to process!:haha So you weren't trying to diagnose the 1689 by doing the pressure test, the code set after/because of the test, correct? It's amazing the amount of good info you collect/generate and post.:thumbsup I NEVER leave here without learning something. Once again, good job!:happymugs
 

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2nd Gen Guru
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2,641 Posts
Discussion Starter #5
I can't seem to find the proceedure but it request that you pull the fuel pump relay from the PDC to do the cranking fuel pressure test.

When I was completeled the code was tripped... So it was a learning curve for me...
 

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i didn't look it up, but i believe thats what my truck threw when the suspect was the Throttle Positions Sensor (APPS) the truck would just cut out but stay running at an idle..... i'm not 100% sure....

are there any symptoms beside just having the code?
 

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2nd Gen Guru
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2,641 Posts
Discussion Starter #7
i didn't look it up, but i believe thats what my truck threw when the suspect was the Throttle Positions Sensor (APPS) the truck would just cut out but stay running at an idle..... i'm not 100% sure....

are there any symptoms beside just having the code?
APPS codes (P0121, P0122, P0123). APPS codes will alow the truck to run but no throttle change.

P1689 No Comm between VP44 and ECM. The engine won't even start...
 
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