Got that pesky yellow Check Engine Light on your REM? Fear not, for now you have the power to vanquish those stubborn Renix Electrical Gremlins once and for all!
REM Codes
These codes come from analyzing the data stream in real time to catch sensor faults.
- MAP Sensor Low:
Manifold Air Pressure Sensor reading is too low.
Possibly disconnected MAP Plug or Short to Ground. - MAP Sensor High:
Manifold Air Pressure Sensor reading is too high.
Possibly disconnected Vacuum Line or Bad Ground. - Baro Pressure Low:
Manifold Air Pressure Sensor reading is too low during Key On, Engine Off.
Possibly clogged or check valve on MAP Vacuum Line, or Low 5V Reference Voltage. - Water Temp Low:
Coolant Temperature Sensor reading is too low.
Possibly disconnected CTS Plug or wiring. - Water Temp High:
Coolant Temperature Sensor reading is too high.
Engine is too hot, or Possibly CTS is shorted to Ground. - Air Temp Low:
Intake Air Temperature Sensor reading is too low.
Possibly disconnected IAT Plug or bad wiring. - Air Temp High:
Intake Air Temperature Sensor reading is too high.
Possibly disconnected IAT Plug or short to ground. - Battery Voltage Low:
Battery Voltage is too low.
Check Alternator Output, Possibly weak wiring to ECU. - Battery Voltage High:
Battery Voltage is too high.
Check Alternator Output, Possibly damaged ECU. - Battery Crank Weak:
Battery Voltage while engine cranking is too low.
Check Battery Health and Charge, Possibly weak wiring to Starter. - o2 Sensor Low:
Oxygen Sensor reading is stuck low.
Possibly engine is extremely rich, possible short to ground. - o2 Sensor High:
Oxygen Sensor reading is stuck high.
Likely Dead o2 sensor, possibly o2 Disconnected or engine is extremely lean. - o2 Heater Voltage Low:
Oxygen Sensor Heater Relay Voltage is too low.
Possibly faulty o2 Relay, ECU stuck in WOT mode. - Loop Fault Rich:
ECU Closed Loop Attempt failed, too rich to correct.
Possibly too large injectors, other fuel system imbalance. - Loop Fault Lean:
ECU Closed Loop Attempt failed, too lean to correct.
Possibly faulty o2 sensor, weak fuel pressure, other fuel system imbalance.
– TIP: This code is more common during cold weather starts as the first Closed Loop attempt may fail due to the Cold Fuel Enrichment value still being too high. This code can be ignored if the 2nd closed loop attempt succeeds. - CPS Crank Fault:
No Engine RPM Detected after 3 seconds of starter engagement.
Possibly faulty CPS, engine cranking speed too low. - RPM Idle Low:
Engine Idle RPM too low.
Possibly damaged IAC valve, dirty Throttle Body, TPS adjustment off. - RPM Over Rev:
Engine RPM too high.
Engine was revved over 5,000 RPM Redline - TPS Too Low:
Throttle Position Sensor reading is too low.
Adjust sensor to 17% closed, possibly disconnected, or short to ground. - TPS Too High:
Throttle Position Sensor reading is too high.
Possibly out of adjustment, or bad ground. - Knock Too High:
Engine Knock Sensor value is too high.
Possibly bad fuel, too low octane, or mechanical engine issue. - Knock Sensor Fault:
Engine Knock Sensor does not change.
Possibly bad Knock Sensor or wiring. - Distributor Sync:
Engine Distributor Sync Sensor does not change.
Possibly bad Distributor Sync Sensor or wiring.
– Tip: This code may incorrectly trip during highway cruising when the data rate update speed matches the engine rpm causing the sync reading to appear dead. If the sync reading changes when the engine RPM is changed, this code can be ignored. - Injectors Weak:
Engine Fuel Injectors are being commanded open too long, Duty Cycle over 80%.
Possibly injectors are too small, weak fuel pressure, other fuel system imbalance.
ECU Codes
These codes come from the 4.0L ECU’s internal Power On Self Test mode. They only run once when the key is turned from Off to Run and can be a little unreliable.
- No Injector 12V
ECU did not detect 12V on Injector feed wire.
-TIP: If this code shows with “KO Tests Not Run,” it can be ignored. - 12V Injector Hot
ECU detected 12V on Injector feed wire when it wasn’t requested. - No Injector GND
ECU did not detect Injector ground path. - Injector # Short
ECU detected Injector # wire has a short to ground. - Injector # Open
ECU does not detect Injector # wire has a ground path. - Water Temp Sensor
ECU does not detect the Coolant Temp Sensor or path to ground. - KO Tests Not Run
ECU did not run the Key On Self Test. - Fuel Not Primed
ECU did not prime fuel pump before start. - ICM Signal Open
ECU did not detect connection to Ignition Coil Module. - EGR Solenoid Open
ECU did not detect connection to Exhaust Gas Recirculation Solenoid or path to ground. - B+ Relay Open
ECU did not detect connection to B+ Relay coil or path to ground. - o2 Relay Open
ECU did not detect connection to Oxygen Sensor Heater Relay coil or path to ground. - A/C Relay Open
ECU did not detect connection to A/C Compressor Relay coil or path to ground.