P0688 on RAM: How to Diagnose & Fix
ECM/PCM Power Relay Sense Circuit/Open
1 RAM model · 1 documented issue · 1 critical · $300-$1,200 repair
P0688 on RAM by model: symptoms, diagnosis and fix
The TIPM is the central under-hood fuse/relay and power-distribution computer that controls the fuel pump, lighting, wipers, door locks, horn, and trailer-tow circuits. It is a widespread failure point on 2007-2016 Ram trucks. The most common complaint is the internal fuel pump relay sticking: stuck ON causes overnight battery drain and the pump running with the key off, while stuck OFF causes intermittent no-start / stalling. Other failures include inoperative wipers, dead door locks, non-working turn signals/high beams, phantom horn, and dead trailer lights. Root causes include water intrusion into the layered module and improperly spliced aftermarket accessories overloading circuits.
Common Symptoms
- No-start or intermittent crank-no-start
- Fuel pump runs with key off / dead battery overnight
- Wipers, door locks, or horn inoperative
- Turn signals or headlights not working
- Trailer tow lights dead
- Random electrical gremlins / stalling
How to Fix
Diagnose which circuit is affected before replacing. A stuck fuel pump relay can be temporarily addressed with an external fuel-pump relay bypass harness, but the durable fix is to rebuild the existing TIPM (specialist shops like Circuit Board Medics repair the boards/relays) or replace it with a new module that must be programmed to the VIN. Remove any improper accessory splices feeding off TIPM circuits. Inspect for and seal water intrusion at the module.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- 2006-2009 Dodge Ram TIPM exchange service
Selected 2006-2009 Dodge Ram 1500/2500/3500/4500/5500 applications; VIN, original part number, options and stated exclusions must be checked. Core return applies.
- Dorman 599-914 remanufactured TIPM
Requires scan-tool programming and adaptive learning; verify original module number and configuration.
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Sources for this issue (3)
P0688 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0688 mean on a RAM?
P0688 stands for "ECM/PCM Power Relay Sense Circuit/Open." An open or general fault in the sense (feedback) circuit the module uses to verify the ECM/PCM power relay output. The module cannot confirm relay power is present. On RAM it is documented across 1 model: 2500.
What are the most common causes of P0688?
The most common causes of P0688 are: Open in the power relay sense circuit, Faulty ECM/PCM power relay, Corroded/damaged connectors, Blown fuse on the sensed feed, Internal PCM fault. The specific cause varies by vehicle.
How much does it cost to fix P0688 on a RAM?
Published repair estimates on RAM range from $300 to $1,200 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0688 on a different make?
View P0688 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.