P23E0 judges the effect of the cylinder 4 heater rather than its wiring: the circuit is intact, but the heat delivered or the temperature reached falls short of what the conditions call for. One factor specific to resistive heaters is supply voltage. Bosch specifies 260 W per heating element at 12 V; since power falls with the square of voltage, a weak battery at 10 V during cranking leaves only about 180 W, and warm-up takes noticeably longer. A performance code on one cylinder alone, however, points to that heater: an aged element, deposits or a poor contact. The engine control sets the heating demand from ethanol content and outside temperature, so the fault shows mainly in cold weather on high-ethanol fuel. No manufacturer documents P23E0; CARB expects functional monitoring.
Low severity. Can I keep driving?You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.
Cylinder 4 is numbered according to the manufacturer: check your engine's manual before working on it.
Symptoms
- Rough start in cold weather on high-ethanol fuel
- Longer cranking
- Engine warning lamp, depending on manufacturer
Most likely causes
- Aged heater at cylinder 4 with reduced output
- Poor contact in the cylinder 4 heater circuit
- Weak battery or low system voltage during heating
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: hard
- It affects emissions.
What each character of P23E0 means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- 3: Ignition and misfires
- E0: Specific fault in that system
Frequently asked questions
Can I keep driving with code P23E0?
You can normally keep driving. If it affects the fuel level, do not trust the gauge and refuel earlier than usual.
What causes code P23E0?
The most common causes are: aged heater at cylinder 4 with reduced output; poor contact in the cylinder 4 heater circuit; weak battery or low system voltage during heating.
Related codes
- P23DDCylinder 4 Fuel Heater Control Circuit/Open
- P23DECylinder 4 Fuel Heater Control Circuit High
- P23DFCylinder 4 Fuel Heater Control Circuit Low
- P23DCCylinder 3 Fuel Heater Performance
- P23D4Cylinder 1 Fuel Heater Performance
Sources
- bosch-mobility.com: flex fuel system
- bosch-mobility.com: fuel rail flex fuel
- law.cornell.edu: 13 CCR 1968.2
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.