Checker Marathon B1805 Engine Trouble Code
What is Checker Marathon B1805?
Checker Marathon B1805 indicates potential catalytic converter failure. If completely failed, your vehicle may not run properly and fuel economy will suffer significantly. Average replacement cost is $2,000–$2,140. This repair requires professional service and should not be delayed.
B1805 on the Checker Marathon
In cold climates, Checker Marathon vehicles frequently log B1805 during the first winter of ownership. Condensation inside the throttle body creates a temporary short circuit in the position sensor wiring, which clears once the engine warms up — but the fault code remains stored.
Code Information
| Code Type: | OBD-II Body (B) Trouble Code |
| System: | Body |
| Vehicle: | Checker Marathon |
| Brand: | Checker |
| Model: | Marathon |
| Code: | B1805 |
B1805 Checker Marathon Symptoms
Check Engine Light
Illuminated Checker Marathon dashboard warning
Engine Stalling
Engine stops unexpectedly or misfires
Performance Issues
Reduced power or acceleration on the Checker Marathon
Starting Problems
Difficulty starting the engine
Poor Fuel Economy
Increased fuel consumption on the Checker Marathon
Increased Emissions
Failed emissions test due to B1805
B1805 Code Structure
Understanding what each digit means in the B1805 body trouble code:
| B | 1 | 8 | 0 | 5 |
|---|---|---|---|---|
| Body Code | Fuel And Air Metering | Engine Oil Temperature Sensor Malfunction | Cold Start Injector 1 Malfunction | Crankshaft Position Sensor B Circuit Malfunction |
How to Fix Checker Marathon B1805
Diagnostic Steps:
The catalytic converter has oxygen sensors before and after it. When warm and in closed-loop mode, the upstream O2 sensor reading should fluctuate, while downstream should remain steady.
Repair Solution:
Verify all electrical connections are clean and tight. Check for damaged wiring, especially in high-heat or high-vibration areas. Use manufacturer wiring diagrams for accurate diagnosis.
Technical Notes:
B1805 on electronically controlled automatic transmissions relates to shift solenoid operation. The solenoid actuates hydraulic circuits controlling clutches or bands for gear changes.
Checker Marathon B1805 Repair Cost
A fuel pressure regulator replacement on the Checker Marathon runs $180–$320 at a specialist. Fuel system work requires depressurisation procedures, so this is not typically a DIY job. Some workshops include a full fuel injector flow test (value: $80) at no extra charge.
B1805 Description
B1805 engine trouble code is related to Crankshaft Position Sensor B Circuit Malfunction.
Main Cause
The primary reason for B1805 OBD-II Engine Trouble Code is: Engine Oil Temperature Sensor Malfunction.
Common B1805 Misdiagnosis on the Checker Marathon
A catalytic converter is often condemned on the Checker Marathon when B1805 appears and an efficiency code is present. Before replacement, verify that the upstream oxygen sensor is not slow-responding — a lazy O2 sensor mimics catalytic inefficiency perfectly.
DIY Repair Guide: B1805 on Checker Marathon
The fuel pressure test on the Checker Marathon requires a Schrader-valve type fuel pressure gauge ($25–$40) connected to the fuel rail test port. With the ignition ON (engine off), pressure should hold above 30 PSI for two minutes. A rapid drop confirms a leaking injector or failing regulator as the root cause of B1805.
Preventing B1805 on the Checker Marathon
For diesel Checker Marathon owners, a DPF (Diesel Particulate Filter) regeneration run on the motorway every 500 miles prevents soot blockage that back-pressures the exhaust and forces B1805 flags via the pressure differential sensors.
Frequently Asked Questions — Checker Marathon B1805
A: Contaminated or low-octane fuel can temporarily trigger B1805 through knock retard and lean/rich excursion events. If the code appeared shortly after a fill-up at an unfamiliar station, running the tank close to empty and refuelling with premium is a sensible first step.