Fuel Injector Group B Supply Voltage Circ Low


The PCM has detected a voltage reading in the fuel injector voltage supply circuit (for a particular group of fuel injectors) that does not conform to the manufacturer’s reference value. Typically fuel injector groups are divided into a separate one for each engine bank. Group B normally denotes the injector group for engine bank 2 (engine bank 2 usually contains the number 2 cylinder). Consult the manufacturer’s service manual for which group of injectors that “Group B” represents (as well as acceptable reference voltage limits and/or resistance levels, as well as the location of the number 2 cylinder).

Code Set Parameters

Voltage variations (caused by inadvertent resistance) that exceed 10-percent of the manufacturer’s referenced voltage will cause a code to be stored in the PCM and a malfunction indicator lamp to be illuminated.


These could include a delayed cold start, smoke from the exhaust at start up, rough engine idle, or choppy acceleration. An engine misfire code may also be stored in conjunction with this code and a service engine soon lamp may be illuminated. Some applications will require multiple failure cycles in order for a malfunction indicator lamp to be illuminated others will illuminate the lamp on the initial failure.

Common Causes

The most common cause of this code is damage to wiring caused by wildlife. The warm area atop the engine provides shelter for small animals, where they proceed to gnaw the wiring for some strange reason. Other causes include one or more faulty fuel injectors, corroded electrical wiring or connector faces, a faulty fuse or relay, or a faulty fuel injector driver in the PCM.

Common Misdiagnosis

Keep in mind that PCM failure is rare. Often the PCM is replaced in error because of open or shorted circuits in the fuel injection system.


  • The majority of modern automotive fuel injectors are actuated via a locking two-wire electrical connector
  • They are supplied with a constant supply of voltage (comparable to that of the battery), through a fused power wire
  • The circuit is completed by the second wire which is grounded by the fuel injector driver in the PCM (or other suitable controller) in the form of regulated pulses
  • When the circuit is completed, the fuel injector is activated and a spray of fuel is injected into the individual cylinders (multi-port fuel injection) or throttle body (throttle body injection). A scanner (or code reader), a digital volt/ohmmeter, a suitable “noid lamp” and a manufacturer’s service manual (or the equivalent) will be helpful in successfully diagnosing this code-storing condition. Begin your diagnosis with a visual inspection of all wiring and connectors
  • Repair or replace damaged, disconnected, shorted, or corroded wiring, connectors, and components as necessary
  • Always retest the system after repairs are completed to ensure success. If all system wiring, connectors, and components (Including fuses) appear to be in normal working order, connect the scanner (or code reader) to the diagnostic connector and record all stored codes and freeze frame data
  • This information can be extremely helpful in diagnosing intermittent conditions that may have contributed to this code being stored
  • After the codes are cleared, operate the vehicle to see if the code returns
  • If the code fails to immediately return, you may have an intermittent condition
  • Intermittent conditions can prove to be quite a challenge to diagnose and in extreme cases may have to be allowed to worsen before a correct diagnosis can be made. Use the digital volt/ohmmeter to test the constant power supply to the particular fuel injector group (key on-engine off)
  • If there is no battery voltage detected at the fuel injector group connector, check system fuses and relays
  • Repair faulty components as required, clear the code and retest the system to ensure that the repair was successful
  • NOTE: Carefully test fuses under load
  • Fuses that appear to be working normally with the key on and the engine off may fail when the engine is cranked
  • Poor connections in the fuse panel can often be contributed to this condition
  • If the fuses and relays appear to be intact, disconnect the connector from the PCM (and other related controller/s) and perform a continuity and resistance test on all related circuits
  • Repair or replace open or shorted circuits, connectors, or components as required
  • Clear the codes and test drive the vehicle to ensure a successful repair
  • If the power supply is present at the fuel injector connector/s or harness connector/s, use a “noid lamp” to check for a ground pulse from the PCM
  • If no ground pulse is detected, disconnect the electrical connector from the PCM (and other related controller/s) and perform a continuity and resistance test on all circuits
  • Repair open or shorted electrical wiring, connectors, or components as required then clear the code and retest the system
  • If all circuits appear to be intact, suspect a faulty injector driver in the PCM
  • PCM failure is rare and replacement will require reprogramming of one or more controllers. If a constant power supply and a ground pulse are present, use a listening device to determine whether the injector or injectors in question are being activated
  • This will help you to determine if individual injectors are functioning and spraying fuel into the cylinder
  • If an audible “ticking” noise is heard when the injector is energized, the injector is likely to be operating normally (unless flow is restricted)
  • If no audible tick is heard when the injector is energized, suspect a faulty fuel injector
  • Remove the electrical connector from the injector and perform a resistance test on the injector
  • Compare your actual findings with manufacturer’s specifications and replace injector/s (with o-rings if applicable) as necessary
  • As always, clear the codes and test drive the vehicle afterwards to ensure that a successful repair has been completed
  • If an audible tick is heard when the injector is energized, remove the injector from the engine and carefully observe the fuel spray pattern as the injector is energized
  • If the spray is acceptable, suspect a faulty PCM as the cause of this code
  • If the fuel spray is restricted or non existent, replace the injector/s in question
  • After the injector/s are replaced clear the codes and test drive the vehicle to make sure that your repair was successful