P35B1

Cylinder 3 Injector Circuit Low

P35B1 is a generic OBD-II powertrain diagnostic trouble code: Cylinder 3 Injector Circuit Low. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P35B1
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on, possible limp mode)
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What P35B1 means

P35B1 indicates the ECM has detected a below-threshold voltage or current level on the injector control circuit for cylinder 3. The module compares its commanded drive signal against measured feedback to detect open or short conditions, and a persistently low reading sets this fault code.

A short to ground in the harness between the ECM and the cylinder 3 injector is among the most frequent causes, as is a failed injector solenoid. Because the third cylinder is not receiving properly timed fuel pulses, driveability symptoms such as misfire, rough idle, and increased emissions will accompany this code. In some calibrations the ECM will disable fueling to the affected cylinder and activate a reduced-power mode.

Diagnosis should follow a logical electrical testing sequence: visual inspection first, followed by resistance measurement of the injector, continuity testing of the harness, and finally evaluation of the ECM driver if all external components test good. Replacing parts without completing this sequence risks unnecessary expense and may leave the true cause unresolved.

Common causes

Most-frequently reported root causes when P35B1 is logged.

  • 1
    Short circuit to ground in the cylinder 3 injector wiring.
  • 2
    Injector solenoid winding failure producing abnormally low resistance.
  • 3
    Corroded or damaged cylinder 3 injector connector terminals.
  • 4
    Wiring chafing against engine components causing a grounding fault.
  • 5
    Faulty ECM injector driver channel for cylinder 3.
  • 6
    Wrong injector impedance due to incorrect part installation.
  • 7
    Fuel or coolant contamination causing connector tracking shorts.

Symptoms drivers notice

MIL illuminated with a cylinder 3 injector or misfire code stored.
Rough idle, hesitation, or misfire under acceleration.
Reduced engine power, possibly with limp-mode engagement.
Elevated hydrocarbons visible during emissions testing.
Possible cylinder 3 misfire code stored concurrently.

How to diagnose P35B1

A typical diagnostic flow when this code is present.

  1. 1
    Scan for all codes and record freeze frame data before clearing anything.
  2. 2
    Visually inspect the cylinder 3 injector connector and harness routing for damage.
  3. 3
    Measure the resistance of the cylinder 3 injector solenoid and compare to spec.
  4. 4
    Check the injector signal circuit for a short to ground with the injector disconnected.
  5. 5
    Monitor live fuel trim and injector pulse width data to quantify cylinder imbalance.
  6. 6
    Swap the injector with a known-good one and retest to confirm or exclude the injector.
  7. 7
    If external components pass, perform an ECM driver output test with a scope before replacing the module.

Related powertrain codes

Frequently asked questions

Can P35B1 cause a P0303 misfire code to appear simultaneously?

Yes. If the injector circuit fault prevents fuel delivery to cylinder 3, the ECM will also detect the resulting misfire and log a P0303 alongside P35B1.

Does P35B1 always point to the injector itself?

No. The code describes a circuit fault, which means the wiring, connector, or ECM driver could be responsible. Test the circuit systematically before replacing the injector.

How urgent is this repair?

It should be treated as soon as reasonably possible. Continued misfiring can overheat and damage the catalytic converter, adding significant repair cost.

Can a bad ground cause P35B1?

A high-resistance or missing ECM ground can affect multiple injector circuits simultaneously. If more than one cylinder shows low-circuit codes, check ECM power and ground circuits first.

Disabling P35B1 in software

RaceTune can permanently disable P35B1 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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