P0606
A control module found a fault in its own processor or programming
Severity: Inspect soonEngine computer (ECM/PCM) codes
The engine computer (ECM or PCM) runs fuel, spark and emissions control and also checks itself: its memory, its processor, its programming and the regulated voltage it supplies to sensors. US and California OBD rules require it to turn on the check engine light when it detects a fault in itself or falls back into a limp-home mode. Many of these codes are caused by something outside the computer, so it should be the last part replaced, not the first.
How these codes differ
- Internal-fault codes (for example P0601 memory check, P0604 and P0605 RAM and ROM, P0606 processor) mean the computer failed its own self-test. Before condemning it, check its power feeds, grounds and battery voltage, because a poor supply can make a healthy computer fail a self-check.
- Sensor reference voltage codes (P0641, P0651 and P0697 for reference circuits A, B and C, and the low or high versions after them) mean the steady 5-volt supply the computer feeds to several sensors is out of range. One supply often feeds several sensors, so a single shorted sensor or chafed wire can pull it down and make every sensor on that circuit look faulty.
- Programming and identity codes (for example P0602 programming error, P0630 VIN not programmed) are about the software rather than hardware. The rules require each computer to report a calibration ID and a calibration verification number, which a technician can compare with the carmaker's latest software.
- Output-driver and module-to-module codes in the P06xx range report that the computer could not control a circuit or confirm a value it was meant to. They point to that circuit's wiring and load first, then to the driver inside the computer.
Codes that show up together
- A sensor reference voltage code (P0641, P0651 or P0697) together with codes for several different sensors at once: suspect the shared 5-volt supply. Unplugging the sensors on that circuit one at a time until the reference voltage recovers finds the one dragging it down.
Engine computer (ECM/PCM) codes
P0607
A control module failed one of its internal performance checks
Severity: Inspect soonP061B
Engine computer’s internal torque calculation check failed
Severity: Inspect soonP06DD
Oil pump pressure control not responding, as if stuck off
Severity: Inspect soonP0601
Control module internal memory checksum error
Severity: Inspect soonP061A
Engine computer internal fault: torque monitoring performance
Severity: Inspect soonP0685
ECM/PCM power relay control circuit open
Severity: Inspect soonP06DA
Oil pressure control solenoid circuit open or high resistance
Severity: Inspect soonP1603
Engine stall history (Toyota)
Severity: Inspect soonP1605
Rough idling (Toyota)
Severity: Inspect soonP2615
Camshaft position signal output circuit voltage low
Severity: Inspect soonP0600
Engine computer lost communication with another module
Severity: Inspect soonP0605
The engine computer failed its own read-only memory check
Severity: Inspect soonP060A
The engine computer's monitoring processor reports a performance fault
Severity: Inspect soonP068A
Engine computer power relay switched off too early
Severity: Inspect soonP06DE
Engine oil pressure control circuit stuck on
Severity: Inspect soonP2638
Engine and transmission computers disagree on the torque signal
Severity: Severity not verifiedP0651
The 5-volt reference supply (circuit B) that powers a group of sensors is out of range
Severity: Inspect soonP2610
The engine computer internal engine-off timer is not performing as expected
Severity: MonitorP061C
Engine computer reports a fault in its own engine speed check
Severity: MonitorP0688
Engine computer power relay sense circuit fault
Severity: Inspect soonP06B8
Engine computer reports a fault in its non-volatile memory
Severity: MonitorP0604
Internal memory (RAM) fault inside the engine or powertrain control module
Severity: Inspect soonP0641
The 5-volt reference supply (circuit A) that powers several engine sensors is out of range
Severity: Inspect soonP0657
Actuator supply voltage circuit open or out of range: the module that powers the engine and throttle actuators sees a problem with their supply
Severity: Inspect soonP00FF
Body control module asked for the check engine light to be turned on
Severity: Severity not verifiedP032F
The engine is producing less torque than the computer expects
Severity: Severity not verifiedP0602
Control module programming error
Severity: Inspect soonP0603
Control module keep alive memory error
Severity: Inspect soonP0608
The engine computer found a fault in the speed signal it sends out to other systems
Severity: Severity not verifiedP0609
The engine computer cannot pass its vehicle speed signal (output B) to other modules
Severity: Severity not verifiedP060C
The engine or vehicle computer found a problem with its own main processor
Severity: Inspect soonP062F
A control module found an error in its own stored memory (EEPROM)
Severity: Inspect soonP0643
The sensor reference voltage A circuit reads too high
Severity: Inspect soonP0650
Check engine light circuit fault: the engine computer sees a problem in the circuit that switches the malfunction indicator lamp
Severity: Severity not verifiedP0653
The engine computer sees too much voltage on its sensor reference supply B
Severity: Inspect soonP0655
The engine computer found a fault in the circuit that drives the engine-hot warning lamp
Severity: Severity not verifiedP0656
The engine computer found a fault in the fuel level output circuit that feeds the fuel gauge signal
Severity: Severity not verifiedP2509
The engine computer's power supply is dropping out on and off
Severity: Inspect soon
Sources and review
- Final Regulation Order: 13 CCR §1968.2, Malfunction and Diagnostic System Requirements (OBD II), 2004 and subsequent model-year passenger cars, light-duty trucks and medium-duty vehicles (2015 amendments)
- Automotive Polygamy (shared 5-volt sensor reference circuits)
- Diagnostic Trouble Codes Explained: How to Manage DTCs
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error