P2511

Code

Generic P — Powertrain

ECM/PCM Power Relay Sense Circuit Intermittent

Brand: Generic

Type: P — Powertrain

Views: UK: 20 EN: 30 RU: 24

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Causes

Faulty ECM/PCM power relay (weak contacts or intermittent coil)
Loose, corroded, or damaged wiring or connectors on the relay sense circuit
Poor battery positive connection or weak battery
Intermittent main power fuse or fusible link
Poor or corroded PCM power/ground connections
Aftermarket electrical accessories drawing excessive current or creating noise

Symptoms

Malfunction Indicator Lamp (MIL) ON with P2511 stored
Intermittent no-start or stalling
Random or intermittent loss of engine management functions
Erratic sensor readings or drivability issues
Possible multiple unrelated DTCs when PCM loses power

What to check

Retrieve freeze frame and freeze data with a scan tool; note conditions when code set
Check battery voltage (resting and while cranking) and charging system output
Visual inspection of ECM/PCM power relay, fuse(s), fusible link, and associated connectors for corrosion, looseness or heat damage
Wiggle test harnesses and connectors while monitoring relay sense voltage or while scanning for code reappearance
Backprobe relay sense circuit at relay and at PCM to compare voltages
Swap relay with identical known-good relay (if available) to see if code returns

Signal parameters

Expected: Relay sense circuit should show battery voltage (approx. 12–14.5 V) when key ON and remain steady while engine is running
During cranking: voltage should remain above roughly 9–10 V (engine start condition) without rapid dropouts
Intermittent condition: voltage spikes, drops to 0 V, or rapid pulses on the sense line indicating open/short or intermittent connection
Resistance: continuity from PCM sense pin to relay output/battery should be low (near 0 Ω) when relay is closed

Diagnostic algorithm

Clear codes and attempt to re-create the failure; note whether P2511 returns and under what conditions (key ON, cranking, running, load).
Check battery state of charge and charging system; confirm battery terminals are clean and tight.
Inspect power relay, fuse(s) and fusible link for damage, melting, or corrosion. Replace suspect fuse/relay with known-good units for test.
With a digital multimeter, backprobe the relay sense input and the PCM power-supply pin while creating the fault (wiggle test). Look for voltage drops, intermittent opens or noise.
If intermittent is not found with DMM, use a lab scope to capture transient dropouts or pulses on the sense circuit while operating key/cranking/engine running.
If wiring shows intermittent continuity, repair or replace the harness section, terminals, or connector(s). Ensure proper pin fit and corrosion protection.
Verify all PCM ground and battery positive connections are clean, tight and free of corrosion. Repair grounds as needed.
Re-test after repairs; if wiring, relay and power supply checks are good and intermittent remains, consider PCM bench testing or replacement as a last step per manufacturer procedure.

Likely causes

Intermittent relay contacts or failing relay
Loose or corroded connector at relay or PCM
Wiring abrasion/chafe causing intermittent open/short
Low battery voltage or marginal charging system
Intermittent fuse/fusible link or weakened terminal

Fault status

⚠️ Status

ECM/PCM Power Relay Sense Circuit Intermittent — PCM detected intermittent or unstable voltage on the power relay sense circuit that supplies the PCM.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.5 - 3.0 hours