P0688 on 2006-2018 RAM 2500 (2500) — ECM/PCM Power Relay Sense Circuit/Open
1 vehicles · 1 makes · $300-$1,200 repair
Most Reported On
P0688 is an OBD-II diagnostic trouble code meaning “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. This code is most commonly reported on 2006-2018 RAM 2500 (2500), with repair costs ranging from $300 to $1,200.
Common Causes
Typical Repair Cost
Based on 1 documented vehicle-specific issues. Actual cost depends on root cause and vehicle.
Diagnostic Tools
To diagnose P0688, you'll need an OBD-II scanner. Here are our recommendations at every price point.
ANCEL AD310 Classic OBD-II Scanner
by ANCEL
A simple, affordable code reader that reads and clears check engine codes. Great for quick diagnostics on any OBD-II vehicle (1996+).
- Read & clear engine codes
- View freeze frame data
- I/M readiness status
- No batteries or app needed
BlueDriver Pro Bluetooth Scanner
by BlueDriver
Bluetooth OBD-II scanner with a free companion app. Provides enhanced diagnostics, smog readiness, and repair reports sourced from a database of verified fixes.
- Enhanced diagnostics (ABS, SRS, transmission)
- Repair Reports with verified fixes
- Smog check readiness
- Free app (iOS & Android)
LAUNCH CRP123X OBD-II Scanner
by LAUNCH
A professional-grade handheld scanner that reads all four major systems (engine, transmission, ABS, SRS) with live data streaming and graphing.
- Engine, transmission, ABS, SRS diagnostics
- Live data stream & graphing
- AutoVIN for vehicle identification
- Free lifetime updates via Wi-Fi
Autel MaxiCOM MK808S Diagnostic Tool
by Autel
Shop-level diagnostic tablet with bi-directional control, active tests, and full system coverage. Ideal for serious DIYers and small shops.
- All-system diagnostics (25+ modules)
- Bi-directional control & active tests
- Oil reset, EPB, BMS, TPMS, injector coding
- 7-inch touchscreen with Android OS
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FAQ
What does P0688 mean?
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.
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?
Repair costs for P0688 range from $300 to $1,200, depending on the vehicle and root cause.
Which vehicles are affected by P0688?
Au7o has documented P0688 across 1 vehicle models from 1 manufacturers: RAM.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.