P23CD

Code

Generic P — Powertrain

Fuel Heater Control Module Feedback Signal/Open

Brand: Generic

Type: P — Powertrain

Views: UK: 18 EN: 25 RU: 17

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Read and record freeze frame data and live PID values for fuel heater feedback
Verify related fuses and relays for the fuel heater circuit are present and good
Visually inspect connectors at fuel heater control module and ECM for corrosion, bent pins, or water intrusion
Backprobe the feedback signal wire at the module and at the ECM while commanding heater on/off
Perform a wiggle test of the wiring harness while monitoring the feedback signal for intermittent opens
Measure continuity and resistance of the feedback wire between module and ECM (with battery disconnected where required)

Typical feedback signal: 0–5 V logic range (varies by manufacturer; ECM expects a valid voltage or PWM feedback)
When heater is OFF: feedback ~0 V (or low logic level); when ON: feedback will change toward supply/PWM level (often >3–4 V or recognizable duty-cycle waveform)
Open circuit: infinite resistance or >10 kΩ between signal conductor and ECM/module terminal
Short to ground: near 0 Ω to chassis ground; short to battery: near 0 Ω to +12 V
Connector continuity: low resistance expected (

Retrieve DTC and freeze-frame data with a scan tool. Confirm P23CD is current and note operating conditions.
Inspect visible wiring, connectors and module for damage, corrosion, moisture or loose pins. Repair any obvious problems.
Verify fuses/relays powering the fuel heater control module are intact and that the module has proper battery power and ground.
With ignition on (and following safety/manufacturer instructions), backprobe the feedback signal at the module and at the ECM. Observe voltage at rest and while commanding heater ON via a diagnostic tool. Compare to expected signal behavior.
If no feedback signal is present, measure continuity between the module feedback terminal and the ECM feedback terminal. Repair any open or high-resistance wiring.
If the wiring and connectors are good but no valid feedback appears when the module is commanded, substitute a known-good fuel heater control module if available or bench-test the module per manufacturer procedure.
After repairs, clear codes and perform a functional test: command the heater on/off and verify proper feedback and heater operation during repeatable conditions.
If intermittent, perform a road/test-cycle to confirm the fault does not return. If it does, re-inspect for intermittent wiring faults (chafing, movement points).

Connector corrosion or bent/broken pins at the fuel heater control module
Open circuit in signal/feedback wire (wire chafed, broken at harness flex point)
Fuel heater control module internal failure (feedback output stage open)
Blown fuse or failed power/ground circuit feeding the module