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DTC codes / Chrysler codes / P1291

P1291 · ChryslerNo Temp Rise Seen From Fuel Heaters

P1291 on Chrysler vehicles means the powertrain control module (PCM) commanded the fuel heater circuit on and monitored no corresponding temperature rise from the fuel temperature sensor over a calibrated time window. The PCM expects the fuel heater to warm the fuel in the filter housing, and when the sensor reading stays flat the code is stored and the check engine light is illuminated.

SystemPowertrain
Code typeChrysler specific
SeverityLow
Fix difficultyIntermediate
AreaFuel and air metering (injector circuits)

Symptoms you may notice

  • Check engine light illuminated with no other obvious drivability complaint
  • Hard starting or rough running in cold ambient temperatures below freezing
  • Extended cranking time before the engine fires when the fuel is cold
  • White smoke or poor combustion quality shortly after a cold start
  • Fuel filter housing heater element that stays cold to the touch when the key is on
  • Often no symptoms besides the warning light in mild weather

Common causes, most likely first

  1. Failed fuel heater element inside the fuel filter housing
  2. Open or corroded wiring between the PCM and the fuel heater connector
  3. Blown fuse or failed fuel heater relay in the power distribution center
  4. Fuel temperature sensor reading stuck or biased, so the PCM never sees the rise
  5. Poor ground connection at the fuel heater or filter housing
  6. PCM driver circuit fault for the fuel heater output
  7. Wrong fuel filter housing installed without a functioning heater element

How to diagnose and fix it

  1. Scan all modules and record freeze-frame data for P1291, noting ambient and fuel temperature at the time of failure
  2. Verify battery voltage and inspect the fuel heater fuse and relay in the power distribution center
  3. Disconnect the fuel heater connector and measure resistance across the heater element to confirm it is not open
  4. Backprobe the heater connector with the key on and command the heater on with a scan tool to confirm power and ground are present
  5. Check the fuel temperature sensor reading against ambient temperature after a cold soak to rule out a biased sensor
  6. Inspect the harness from the PCM to the fuel filter housing for chafing, corrosion, or pushed terminals
  7. Replace the failed heater element, sensor, or repair the circuit as indicated, then clear codes and verify the temperature rise with a scan tool

What the fuel heater test really checks

  • The PCM does not measure heater current directly; it infers heater operation from the fuel temperature sensor, so a lazy sensor can set P1291 even when the heater element is good.
  • A fuel heater that works but is slow to warm the fuel can trip this code in very cold weather because the temperature rise falls outside the calibrated time window.
  • Aftermarket fuel filter housings without a heater element are a common cause on older Chrysler diesel trucks, and the connector is often left dangling.
  • P1291 can appear alongside glow plug or intake air heater codes when cold-start strategies are fighting a fuel temperature signal that never changes.
  • Clearing the code without a cold soak and a commanded heater test will usually result in the code returning on the next cold start.

Can I keep driving with P1291?

The vehicle remains safe to drive because the fuel heater only affects cold-weather starting and combustion quality, but avoid extended operation in sub-freezing temperatures until the fault is repaired. If cold starting becomes difficult or white smoke persists, address the heater circuit promptly.

Tools that help

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Guidance is general and written for Chrysler vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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