2003-2009 Infiniti FX35 ABS Light On: Common Causes and Fixes

By Core Brake Parts Tech Team — Circleville, OH warehouse

When the ABS light comes on in a 2003-2009 Infiniti FX35, the most common cause is a wheel speed sensor problem: a failed sensor, a damaged harness or connector, or debris and damage at the sensor rotor that the sensor reads. The FX35's ABS control unit shuts off anti-lock braking and turns on the ABS, VDC OFF and SLIP lights together when it sees an electrical fault, so the fastest path to a fix is reading the stored trouble code before buying any parts. Normal braking still works, but you have lost ABS and stability control until it is repaired.

How the ABS and VDC System Works on the FX35

The FX35 does not have a standalone ABS box. Anti-lock braking (ABS), electronic brake distribution (EBD), traction control (TCS) and Vehicle Dynamic Control (VDC) all run through one component Infiniti calls the ABS actuator and electric unit (control unit). It takes speed signals from all four wheels, plus a steering angle sensor, a brake pressure sensor and a G sensor, and uses the actuator's solenoid valves to modulate pressure at each wheel.

That shared design explains the warning-light pattern owners see. According to the factory service manual for the FX35/FX45:

• ABS electrical fault: the ABS warning lamp, VDC OFF indicator and SLIP indicator all turn on. ABS, TCS and VDC stop working, but EBD keeps working.
• EBD fault: the red brake warning lamp comes on together with the ABS, VDC OFF and SLIP lights, and both EBD and ABS stop working. Treat this one as more urgent.
• VDC/TCS-only fault: only VDC OFF and SLIP turn on, and ABS keeps working normally.

The wheel sensors are active sensors, meaning they need a power supply from the control unit and produce a pulse signal. Up front the sensor reads a magnetic encoder, which the manual calls the sensor rotor rubber, built into the wheel hub and bearing assembly. At the rear the sensor rotor sits at the rear final drive. That matters for diagnosis because a loose bearing or a damaged encoder can set a code just like a dead sensor.

Reading the Warning Lights: What Each Combination Means

On a healthy FX35 the ABS lamp comes on at key-on as a bulb check and goes out after roughly 2 seconds. If it stays on, or comes on while driving, the control unit has stored a code.

One case is not a fault. The service manual notes the ABS, VDC OFF and SLIP lights can come on when the running vehicle is subjected to strong shaking or large vibration, for example on a steep banked road or aboard a ship. If all three lights go out after you restart the engine on a normal road, there is no malfunction.

Common Causes of the ABS Light on a 2003-2009 FX35

1. Wheel speed sensor circuit fault

This is the top cause. The FX35's self-diagnosis splits wheel sensor faults into two types for each corner:

• SENSOR-1 codes (C1101 rear right, C1102 rear left, C1103 front right, C1104 front left): the sensor circuit is open, shorted, or its power supply voltage is abnormal. Think broken wire, corroded connector or a dead sensor.
• SENSOR-2 codes (C1105 through C1108): the control unit cannot identify sensor pulses because the gap between the wheel sensor and sensor rotor is too large. Think loose sensor mount, a sensor that is not fully seated, a damaged or contaminated sensor rotor, or excessive axle looseness.
• C1115 (ABS SENSOR abnormal signal): wheel sensor input is abnormal.

Wheel sensor harnesses on any SUV live a hard life near the suspension. The front sensor wires on the FX35 route through rubber grommets at the shock absorber and body panel, so a grommet that has popped out can let the wire rub or stretch.

2. Damaged or dirty sensor rotor, or a loose wheel bearing

Because the front encoder is part of the hub and bearing assembly, a damaged encoder surface or a bearing with play changes the signal the sensor sees. The manual's inspection steps say to check the front sensor rotor rubber surface for damage, the rear sensor rotor for damage, and the front and rear axles for excessive looseness. It also warns that iron chips or other foreign material on the sensor pick-up or caught in the sensor rotor must be cleaned off during installation, since metal debris disturbs a magnetic signal.

3. Low battery voltage or loose power and ground connections

Code C1109 means the power voltage to the ABS actuator and electric unit is too low. The manual's basic inspection includes making sure the battery positive cable, negative cable and ground connections are tight, then confirming battery voltage has not dropped and the alternator is working. A weak battery can light up several warning lamps at once, so check it before condemning any ABS part.

4. Mismatched or unevenly worn tires

The ABS computer compares the speed of all four wheels. Infiniti's service manual says to change all four tires at a time with the same size, brand and tread pattern, and warns that wheel sensor errors can be detected when tire wear varies widely or the size differs from the original tires. The first diagnostic step for a sensor code is literally to check the tires: pressure, wear and size.

5. Pump motor or control unit failure

Less common, but real. C1111 points to the actuator pump motor or its relay control circuit, and C1110 flags an internal controller failure in the ABS actuator and electric unit. These are the expensive answers, and they should come after sensors, wiring, power and tires have all been ruled out.

How to Diagnose It Step by Step

1. Check the simple things first. The manual tells technicians to check brake fluid level, fluid leaks and booster operation alongside electrical diagnosis. If the red BRAKE light is on too, check the fluid reservoir right away, since low fluid can mean worn pads or a leak.
2. Read the codes with an ABS-capable scan tool. A basic engine-code reader will not see ABS (C-series) codes. Note which wheel and whether it is a SENSOR-1 or SENSOR-2 code.
3. Inspect the tires for correct pressure, matching size and even wear.
4. Inspect the sensor and sensor rotor at the flagged corner: sensor mount tightness, encoder or rotor damage, connector terminals and the harness along its whole run.
5. Do not probe the sensor with an ohmmeter. The FX35 manual specifically says not to measure resistance or voltage between the sensor terminals with a tester, because it is an active sensor. Check harness continuity and the supply voltage at the harness connector instead.
6. Repair, clear codes and drive. After a wheel sensor repair, the ABS, VDC OFF and SLIP lamps may stay on until the vehicle is driven at about 19 mph (30 km/h) or more for about 1 minute. Do that before assuming the repair failed.

The Fix: Which Part, and What to Replace at the Same Time

Match the repair to the code:

• SENSOR-1 code with a good harness and good supply voltage: replace that wheel speed sensor. Remove the sensor before pulling the front hub or rear final drive, as the manual advises, so you do not damage the sensor or its wiring.
• SENSOR-2 code: check the sensor mount, clean the sensor pick-up and mounting hole, and inspect the encoder or sensor rotor. At the front, a damaged encoder or a loose bearing usually means a new hub and bearing assembly.
• Harness damage: repair or replace the sensor lead and reseat every grommet and clip so the wire cannot rub again. The manual notes the harness must not be twisted, and on the front sensor the white line on the harness should be visible from the front.
• Low voltage code: clean and tighten battery and ground connections, then test the battery and charging system.

If you have the wheels off, it is a good time to look at the rest of the brake system. The manual's own precautions note that excessively worn brake components can make the VDC OFF and SLIP lights come on, and worn pads lower the fluid level in the reservoir, which is what trips the red brake light. For 2006-2009 models we carry EBC Greenstuff 6000 front brake pads for the 2006-2009 FX35. For 2003-2005 models, rear options include EBC Yellowstuff rear pads for the 2003-2005 FX35 and EBC GD Sport slotted rear rotors. You can also browse all brake pads and brake rotors. Stick with replacement pads and rotors that match the original size, since Infiniti notes non-standard brake components can affect VDC behavior. The manual lists DOT 3 as the recommended brake fluid for this system, and drained fluid should never be reused.

How hard is the job?

Replacing a wheel sensor or cleaning a sensor pick-up is a driveway job with basic tools, a jack and stands. A front hub and bearing assembly is a moderate job. Diagnosing wiring faults and anything involving the ABS actuator and electric unit, which is part of the brake hydraulic system and needs bleeding and scan-tool procedures, is best left to a shop with Infiniti-level diagnostic equipment. Tighten sensor bolts and all brake hardware to the values in the factory service manual.

Recalls: Is There an ABS Recall for the FX35?

We checked NHTSA's recall records for the 2003-2009 FX35, and none of the listed campaigns are for the ABS system. Most FX35 recalls cover passenger airbag inflators, plus fuel filler hose and lighting campaigns. There is one brake recall worth knowing about: NHTSA campaign 03V476000 (Nissan recall R3020) covers certain 2003 FX35 models whose front brake caliper mounting bolts may not have been tightened adequately. A loose caliper can rotate or separate from its bracket. Dealers tighten the bolts at no charge. It is not an ABS-light cause, but if you own a 2003, enter your VIN at nhtsa.gov to confirm it was done.

Frequently Asked Questions

Is it safe to drive an FX35 with the ABS light on?

With only the ABS, VDC OFF and SLIP lights on, normal braking still works but you have no anti-lock, traction or stability control, so wheels can lock in a hard stop. Drive gently and get it diagnosed soon. If the red BRAKE light is also on, check the brake fluid immediately and have the car inspected before driving it further.

Why are the ABS, VDC OFF and SLIP lights all on at once?

On the FX35 all three systems share one control unit and the same wheel speed signals. When that unit sees an ABS electrical fault it shuts down ABS, traction control and stability control together and turns on all three lights.

Will disconnecting the battery reset the ABS light?

It will not fix the cause. If the fault is still present the light comes back. After a real repair, codes are cleared with a scan tool, and the manual notes you may need to drive at about 19 mph or more for about a minute before the lights go out.

Can worn brake pads turn on the ABS light?

Worn pads do not set the ABS sensor codes directly, but they lower the fluid level in the reservoir, which can turn on the red brake warning lamp, and Infiniti notes excessively worn brake components can make the VDC OFF and SLIP lights come on. Replacing worn pads and rotors is often part of sorting out a warning-light complaint.

Which wheel speed sensor is bad?

Only a scan tool that reads ABS codes can tell you reliably. C1101 is rear right, C1102 rear left, C1103 front right and C1104 front left, and C1105 through C1108 are the matching gap or pulse faults for the four corners.

Do new tires affect the ABS on an FX35?

Yes. Infiniti recommends replacing all four tires together with the same size, brand and pattern. Mismatched sizes or very uneven wear can make the system detect a wheel sensor error.

Sources

1. Infiniti 2007 FX35/FX45 Factory Service Manual, Section BRC (Brake Control System) - VDC/TCS/ABS/EBD description, warning-lamp logic and fail-safe behavior, DTCs C1101-C1115, wheel sensor inspection and installation cautions, tire matching, battery inspection, 19 mph drive after repair, DOT 3 fluid
2. NHTSA Recalls API - 2003 Infiniti FX35 - 2003 FX35 recalls, including the front caliper mounting bolt campaign; no ABS campaigns
3. NHTSA Recalls API - 2007 Infiniti FX35 - 2007 FX35 recalls are airbag campaigns; no ABS campaigns
4. NHTSA Recall 03V476000 - 2003 FX35 front brake caliper mounting bolt recall (Nissan R3020)