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DTC codes / Chrysler codes / P1290

P1290 · ChryslerCNG Fuel Pressure Too High

P1290 on Chrysler compressed natural gas (CNG) vehicles indicates that the powertrain control module (PCM) has detected a fuel pressure reading from the CNG pressure sensor that is higher than the calibrated maximum for the current operating conditions. The PCM compares the actual CNG fuel pressure against expected values and sets this code when the signal indicates excessive pressure, often to protect the fuel system and engine from overpressure damage.

SystemPowertrain
Code typeChrysler specific
SeverityMedium
Fix difficultyProfessional
AreaFuel and air metering (injector circuits)

Symptoms you may notice

  • Malfunction indicator lamp (MIL) illuminated, often with no other noticeable symptoms
  • Rough idle or engine stumble, especially when switching between gasoline and CNG operation
  • Reduced engine power or limp mode if the PCM enters a protection strategy
  • Fuel smell or audible hissing from the CNG system in severe cases
  • Hard starting or no-start on CNG, particularly after refueling
  • Poor fuel economy or increased CNG consumption

Common causes, most likely first

  1. Faulty CNG fuel pressure sensor sending an inaccurate high signal
  2. Sticking or failed CNG pressure regulator allowing pressure to exceed the setpoint
  3. Restricted or kinked CNG return line causing pressure to build up
  4. Contaminated or degraded CNG fuel causing regulator malfunction
  5. Wiring issue (short to voltage, chafed harness) in the pressure sensor circuit
  6. PCM calibration error or internal fault in the pressure control logic
  7. Mechanical failure inside the CNG tank valve or high-pressure regulator assembly

How to diagnose and fix it

  1. Connect a scan tool and verify the CNG pressure sensor reading in live data against a known-good mechanical gauge
  2. Inspect the CNG pressure sensor connector and harness for corrosion, chafing, or loose pins, and repair as needed
  3. Check the CNG pressure regulator for proper operation and replace if it is sticking or leaking internally
  4. Inspect the CNG return line for restrictions, kinks, or blockage and clear or replace as necessary
  5. Test the CNG pressure sensor with a multimeter for proper reference voltage and signal return, and replace if out of specification
  6. Verify fuel quality and drain or filter the CNG if contamination is suspected
  7. Reflash or update the PCM calibration if no hardware faults are found, then clear codes and retest

CNG pressure sensor signal traps to avoid

  • A common misdiagnosis is replacing the CNG pressure regulator when the actual fault is a skewed pressure sensor that reads high only at certain temperatures, so always compare live data to a mechanical gauge.
  • The PCM may set P1290 intermittently if the CNG system is overpressurized during refueling on a hot day, and the code may not return after the tank cools, so check for recent refueling events in freeze frame data.
  • Wiring harness chafing near the CNG regulator is a frequent cause that is often overlooked because the sensor itself tests good on the bench.
  • This code does not always mean the CNG system is unsafe to drive; however, ignoring it can lead to regulator damage and expensive repairs, so address it promptly.
  • On some Chrysler CNG vehicles, a weak battery or low charging voltage can cause false pressure sensor readings, so verify battery and charging system health before condemning CNG components.

Can I keep driving with P1290?

It is generally safe to drive with P1290 illuminated if the vehicle runs normally, but avoid aggressive driving and refueling until the fault is diagnosed. If you notice a fuel smell, hissing, or reduced power, stop driving and have the CNG system inspected by a qualified technician.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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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