Got a warning light and a fault code from your scan tool or mechanic? Type the code below to see what it means in plain English, what to check, and whether a Cost Effective Maintenance product may help once the cause is found. We also tell you straight when it’s a repair job and an additive won’t help.
Injector codes
In plain English: One cylinder is contributing less power, or differently, than expected, so the engine can run unevenly. Dirty injectors are one possible cause; worn injectors, low compression and other faults can also cause it.
Technical detail (for your mechanic)
How it helps / what to do: A cylinder is contributing less or differently than expected. Rule out compression, injector wear and mechanical faults. Where injector deposits are identified, CRD Fuel Enhancer can help clean them; recheck balance / correction values after treatment.
Check first: Balance / correction values in live data; compression or relative compression test; leak-off test; injector circuit.
In plain English: Same as above, on engines with 6 or 8 cylinders: one cylinder is contributing less or differently than expected. Dirty injectors are one possible cause among several.
Technical detail (for your mechanic)
How it helps / what to do: As above for V6/V8 diesels. Rule out compression, injector wear and mechanical faults before treating for deposits.
Check first: Balance / correction values; compression test; leak-off test.
In plain English: The engine's computer has reached the limit of how far it can adjust one injector. Something is making that injector behave differently, and it needs to be found.
Technical detail (for your mechanic)
How it helps / what to do: The ECU has reached an injector adjustment limit; don't assume the injector is dirty. Diagnose the injector and fuel system. Perform only the coding or learning procedure the vehicle manufacturer requires.
Check first: Injector coding correct after any replacement; leak-off test; injector circuit; manufacturer's procedure.
In plain English: The engine is missing a beat: one or more cylinders isn't firing properly. You may feel a shake, rough idle or loss of power. There are many possible causes.
CRD Fuel EnhancerFTC Decarbonizer
Technical detail (for your mechanic)
How it helps / what to do: Many possible causes: injectors, compression, glow plugs, sensors, and on petrol engines ignition. Where injector deposits or combustion carbon are identified, CRD Fuel Enhancer cleans injectors and FTC Decarbonizer helps reduce carbon.
Check first: Glow plugs (cold misfire), compression, injector wiring. Petrol engines: spark plugs and coils.
In plain English: An electrical problem with the wiring or the injector itself. It's a repair job, not something an additive can fix.
Technical detail (for your mechanic)
How it helps / what to do: Electrical fault: wiring, connector or injector coil. No direct additive remedy.
Check first: Injector resistance, wiring harness, ECU driver.
In plain English: The electronics that fire the injectors have a fault. This is an electrical repair.
Technical detail (for your mechanic)
How it helps / what to do: Control module / driver fault. No direct additive remedy.
Check first: Module power and grounds, wiring.
Fuel system & fuel pressure codes
In plain English: Not enough fuel pressure is reaching the injectors. Possible causes include a blocked filter, a weak pump, air leaks or a pressure-control fault, so the fuel supply needs checking.
Technical detail (for your mechanic)
How it helps / what to do: Needs fuel-supply and pressure-control diagnosis. If testing or filter inspection confirms microbial contamination, PMX-145 controls the microbes; it does not replace filters or fix supply faults.
Check first: Fuel filter, lift pump, air leaks, suction control valve, high-pressure pump.
In plain English: Fuel pressure is higher than the computer expects. It could be a pressure-control valve, a sensor or a wiring fault.
Technical detail (for your mechanic)
How it helps / what to do: Needs pressure-control diagnosis. If a control valve is found to be sticking because of deposits, CRD Fuel Enhancer may assist.
Check first: Rail pressure sensor, pressure-relief valve, SCV and wiring.
In plain English: The part that controls fuel pressure isn't keeping it where it should be. It needs diagnosis; sticking from deposits or debris is only one possible cause.
CRD Fuel EnhancerPMX-145
Technical detail (for your mechanic)
How it helps / what to do: Needs pressure-control diagnosis. CRD Fuel Enhancer applies only where deposits are confirmed; PMX-145 only where microbial contamination is confirmed. A damaged valve needs replacing.
Check first: SCV / regulator condition and wiring, filter condition, rail pressure actual vs desired.
In plain English: The fuel filter has detected water. Drain it and find out where the water came from. Water damages fuel systems and can allow microbes to grow.
Technical detail (for your mechanic)
How it helps / what to do: Drain the water separator and identify the water source first. Water alone doesn't mean microbial growth. SOS-18 tests for water, particles and microbial (ATP) contamination. PMX-145 controls microbes; it does not remove water.
Check first: Drain the water separator; WIF sensor; source of water (tank, supplier).
In plain English: The system has found a big drop in fuel pressure, as if fuel is escaping somewhere. Needs checking by a mechanic. Fuel leaks can be a fire risk.
Technical detail (for your mechanic)
How it helps / what to do: Usually a physical leak or injector over-return. No direct additive remedy.
Check first: External leaks, cracked lines, leak-off test, pressure-relief valve.
In plain English: The sensor that reads fuel pressure is giving odd readings. Usually a sensor or wiring problem.
Technical detail (for your mechanic)
How it helps / what to do: Mostly a sensor or wiring fault. Check the electrics and compare actual vs desired pressure.
Check first: Sensor voltage, connector; actual vs desired rail pressure.
DPF (diesel particulate filter) codes
In plain English: The exhaust filter that traps soot (the DPF) is getting full. How it gets cleared depends on how full it is and on the vehicle maker's procedure.
Technical detail (for your mechanic)
How it helps / what to do: Check soot load / restriction severity and follow the manufacturer's procedure: some filters can be cleared by regeneration, others need service. Once the cause is addressed, FTC Decarbonizer and CRD Fuel Enhancer help manage soot formation; they don't guarantee the code won't return.
Check first: Soot load reading, DPF differential pressure sensor and hoses, failed regens, driving pattern, EGR.
In plain English: The engine is cleaning the exhaust filter more often than normal. Extra soot is one possible cause; sensor faults and other problems can also cause it.
Technical detail (for your mechanic)
How it helps / what to do: Abnormal regeneration frequency; don't assume excess soot is the only cause. Where diagnosis finds excess soot from combustion, FTC Decarbonizer is a soot-management option.
Check first: Differential pressure sensor, injector balance, EGR operation, boost leaks.
In plain English: The engine is taking longer than normal to clean the exhaust filter. It needs checking to find out why.
Technical detail (for your mechanic)
How it helps / what to do: Abnormal regeneration duration; diagnose the cause. Where excess soot is a contributor, FTC Decarbonizer is a soot-management option.
Check first: Exhaust gas temperature sensors, DOC condition, interrupted regens.
In plain English: Exhaust is struggling to get through the filter. It may be clogged, or a sensor may be reading wrong.
Technical detail (for your mechanic)
How it helps / what to do: Check restriction severity and the sensor, then follow the manufacturer's procedure. After the cause is addressed, FTC Decarbonizer helps manage soot formation.
Check first: Differential pressure sensor and hoses; soot load reading.
In plain English: The exhaust filter isn't catching soot properly. It may be cracked or damaged.
Technical detail (for your mechanic)
How it helps / what to do: Usually a cracked or removed filter, or a sensor fault. No direct additive remedy.
Check first: DPF physical condition, differential pressure sensor, hoses.
In plain English: The readings suggest exhaust is getting through too easily, which usually means a cracked filter or a loose sensor hose.
Technical detail (for your mechanic)
How it helps / what to do: Points to a cracked DPF or a split / disconnected sensor hose, not soot.
Check first: Sensor hoses, DPF substrate condition.
In plain English: The sensor that measures how full the exhaust filter is has a fault. It needs fixing so the filter can be monitored.
Technical detail (for your mechanic)
How it helps / what to do: Sensor or wiring fault. Fix it before judging soot load.
Check first: Sensor supply and signal, blocked or split hoses.
EGR & turbo codes
In plain English: The valve that recycles some exhaust back into the engine (the EGR valve) isn't letting enough through. Carbon build-up is a common cause, but the valve, cooler or sensor can also be at fault.
Technical detail (for your mechanic)
How it helps / what to do: Diagnose the EGR valve, cooler and sensor. A coked valve needs mechanical cleaning or replacement; FTC Decarbonizer can then help reduce the soot entering the EGR system.
Check first: EGR valve movement, cooler blockage, intake carbon, sensor.
In plain English: The EGR valve (which recycles exhaust gas) isn't working as expected. Carbon build-up is one possible cause; the valve, actuator or sensor can also be at fault.
Technical detail (for your mechanic)
How it helps / what to do: Diagnose the valve, actuator and sensor. Clean or replace as required, then FTC Decarbonizer can help slow re-coking.
Check first: EGR valve and position sensor, vacuum / actuator.
In plain English: The turbo isn't building enough boost, so the vehicle feels flat. Possible causes include boost leaks, actuator faults, turbo damage, restrictions or carbon-related sticking.
Technical detail (for your mechanic)
How it helps / what to do: Possible causes include boost leaks, actuator faults, turbo damage, restrictions or carbon-related sticking. FTC Decarbonizer only fits the carbon-related cause.
Check first: Boost leaks, intercooler hoses, VGT actuator, turbo condition, DPF back-pressure.
In plain English: The turbo isn't performing as expected. Possible causes include boost leaks, actuator faults, turbo damage, restrictions or carbon-related sticking.
Technical detail (for your mechanic)
How it helps / what to do: As above. FTC Decarbonizer only fits the carbon-related cause.
Check first: Boost leaks, VGT actuator, boost sensor.
Oil pressure & oil codes
In plain English: Oil pressure is too low. Stop the engine and get the oil pressure tested before driving further, because this can wreck an engine.
SOS-3 Oil Test KitFlushing Oil Concentrate
Technical detail (for your mechanic)
How it helps / what to do: Test oil pressure with a mechanical gauge first. SOS-3 oil analysis supports diagnosis (fuel dilution, wear and condition) but does not measure pressure. Consider Flushing Oil Concentrate only once adequate circulation and safe operation are established and sludge is identified.
Check first: Oil level and grade, mechanical gauge test, pickup screen, oil pump, bearings.
In plain English: The oil pressure reading doesn't look right. It could be the oil, the sensor, or a mechanical problem, so the pressure needs testing.
SOS-3 Oil Test KitFlushing Oil Concentrate
Technical detail (for your mechanic)
How it helps / what to do: Confirm actual pressure with a mechanical gauge before any treatment. SOS-3 can identify fuel dilution and oil condition; it does not measure pressure.
Check first: Sensor vs mechanical gauge, oil viscosity, filter.
In plain English: The oil pressure sensor or its wiring has a fault. It may not be an actual oil problem.
Technical detail (for your mechanic)
How it helps / what to do: Sensor or wiring fault. Confirm with a mechanical gauge before blaming the oil.
Check first: Sensor, connector, wiring.
In plain English: An electrical fault in the circuit that controls the oil pump's output. This is an electrical repair.
Technical detail (for your mechanic)
How it helps / what to do: Circuit / open fault. Electrical diagnosis; no direct additive remedy.
Check first: Solenoid resistance, connector, wiring, ECU output.
In plain English: The part that controls the oil pump's output isn't responding as expected. Deposits are one possible cause; the solenoid, pump or wiring can also be at fault.
Technical detail (for your mechanic)
How it helps / what to do: Control performance / sticking fault. Diagnose the solenoid, pump and oil pressure first; deposits are only one possible cause.
Check first: Solenoid operation, oil pressure test, oil grade to spec.
In plain English: The engine is low on oil. Top up with the correct oil and find out why it's using or losing oil.
Technical detail (for your mechanic)
How it helps / what to do: Restore the correct level with the specified engine oil and investigate the loss. No additive remedy.
Check first: Leaks, turbo seals, PCV system, level sensor.
In plain English: The engine oil is running hotter than it should. Causes include cooling problems, heavy load, low oil level or a sensor fault.
Technical detail (for your mechanic)
How it helps / what to do: Diagnose the cause first. RMI-25 is only relevant if a coolant-side deposit problem is confirmed.
Check first: Coolant level, oil cooler, oil level, oil temp sensor, load / towing.
Valve timing codes (applicable engines only)
In plain English: The system that adjusts the engine's valve timing isn't working as expected. Only engines with variable valve timing set this code.
Flushing Oil Concentrate
Technical detail (for your mechanic)
How it helps / what to do: Applicable engines only. Assess timing, oil pressure and control (solenoid) faults first. Do not flush before these are checked.
Check first: VVT solenoid and wiring, oil level, grade and pressure, timing.
In plain English: The timing between the top and bottom of the engine is out. Often a mechanical timing problem that needs a mechanic.
Flushing Oil Concentrate
Technical detail (for your mechanic)
How it helps / what to do: Applicable engines only. Check timing chain / belt, tensioner, oil pressure and sensors first. Do not flush before these are assessed.
Check first: Timing chain stretch, tensioner, oil pressure, sensors.
What the labels mean: May assist – deposits confirmed: cleaning could address a contributing cause. Preventive maintenance: helps manage deposits or contamination; doesn’t guarantee the code won’t return. Test / diagnose first: the right product depends on finding the cause. Repair required: no direct additive remedy. If your oil pressure warning is on, stop driving and get the engine checked before using any product.
