C1355 – Increasing pressure solenoid (left rear) (Toyota)

Toyota-specific code — factory diagnostic data

C1355 means your Toyota C-HR has an ABS/VSC/TRC fault that can reduce traction and stability control. You may still have normal braking, but the vehicle can lose assist features during hard stops or slippery roads. According to Toyota factory diagnostic data, this code indicates a problem area related to the increasing pressure solenoid for the left rear brake circuit. This is a manufacturer-specific Toyota chassis code, so the exact test logic and enabling conditions can vary by platform. Treat it as a direction to test the solenoid circuit and hydraulic control actuator operation, not as proof that a part failed.

C1355 Quick Answer

C1355 points to the ABS/VSC/TRC “increasing pressure” solenoid for the left rear channel. Confirm the solenoid circuit integrity and actuator power/grounds before replacing the hydraulic unit.

What Does C1355 Mean?

Official definition: “Increasing pressure solenoid (left rear).” In plain terms, the ABS/VSC/TRC module detected a problem controlling brake pressure on the left rear channel. In practice, the system may disable ABS, VSC, or traction functions because it cannot trust that pressure control.

What the module checks: The ABS/VSC/TRC module commands the increasing-pressure solenoid on and off, then monitors the expected electrical response. Depending on Toyota platform design, it may watch current flow in the solenoid driver, circuit continuity, and plausibility during self-checks. Why that matters: The code points to a suspected trouble area. You still must prove whether the fault comes from wiring, a connector, the hydraulic actuator/solenoid coil, module power/ground, or an internal driver issue.

Theory of Operation

Under normal operation, the Toyota ABS/VSC/TRC hydraulic control actuator uses solenoids and a pump to modulate brake pressure per wheel. The module increases pressure by energizing a specific solenoid valve for that channel. It reduces or holds pressure by commanding other valves, based on wheel speed inputs and stability calculations.

C1355 sets when the module commands the left rear increasing-pressure solenoid but sees an abnormal electrical condition. An open, short to ground, short to power, or high resistance changes the current profile. A poor actuator ground or low system voltage can also disrupt solenoid control and trip the code.

Symptoms

Drivers and technicians usually notice one or more of these symptoms when C1355 sets:

• Warning lights ABS, VSC, and/or TRAC lights illuminated
• Message display stability or traction control warning message on the cluster
• Feature reduction ABS or stability interventions stop working when needed
• Brake feel pedal feel may change during ABS events, or ABS does not pulsate
• Stored codes related ABS/VSC/TRC solenoid or actuator codes may appear with C1355
• Intermittent behavior lights may reset after a key cycle, then return on bumps or turns
• Fail-safe system enters a protective mode and disables hydraulic modulation

Common Causes

• Open circuit in the left rear increasing pressure solenoid control wiring: A broken conductor stops current flow, so the ABS/VSC/TRC module cannot drive or monitor the solenoid correctly.
• Short to ground on the solenoid control circuit: Insulation damage can pull the driver low all the time and trigger a circuit fault during self-checks.
• Short to power on the solenoid control circuit: A rubbed-through harness can backfeed voltage and prevent the module from modulating the solenoid as commanded.
• High resistance at the actuator connector: Corrosion or loose pins raise resistance and distort the module’s current feedback for that solenoid channel.
• Internal fault in the hydraulic brake actuator solenoid coil: A coil winding issue changes electrical load and causes the module to flag the increasing pressure solenoid circuit as implausible.
• Shared power supply or ground issue affecting the actuator: A weak relay feed, poor ground splice, or loose ground point can drop voltage under load and mimic a solenoid failure.
• Water intrusion into the actuator or harness branch: Moisture creates intermittent shorts and unstable resistance that often set the DTC during wet conditions.
• ABS/VSC/TRC module driver fault (actuator assembly electronics): A failed output stage can stop proper current control, but you must prove wiring and solenoid integrity first.

Diagnosis Steps

Use a scan tool that can access Toyota ABS/VSC/TRC data and run active tests. Have a quality DMM, back-probe pins, and wiring repair tools ready. A test light or low-amp current probe helps verify driver operation. Plan for safe wheel-off access and stable vehicle support if you inspect harness routing.

1. Confirm DTC C1355 in the ABS/VSC/TRC module, then record freeze frame data and all related codes. For this circuit-type DTC, focus on battery voltage, ignition state, vehicle speed, and any companion actuator or power supply codes. Clear codes and see if C1355 returns immediately at key-on, since hard electrical faults often do.
2. Check fuses, relays, and power distribution that feed the ABS actuator and ABS/VSC/TRC module before you probe the module connector. Perform a careful visual inspection of the actuator power and ground paths, because a blown fuse or overheated relay socket can create a false “solenoid” code. If you find any power supply DTCs, diagnose those first.
3. Verify ABS/VSC/TRC module power and grounds with voltage-drop testing under load. Command an ABS-related active test or run conditions that energize the actuator, then measure voltage drop from battery negative to module ground and from battery positive to module B+ feed. Keep ground drop under 0.1 V with the circuit operating, because a high-resistance connection can pass a no-load continuity test.
4. Inspect the actuator and harness connectors with a pin-fit and terminal-condition check. Look for spread terminals, bent pins, corrosion, and signs of fluid or water intrusion. Follow the harness a short distance from the actuator to find rubbing points, tight bends, and prior repair splices that can fail under vibration.
5. Use the scan tool data list to compare commanded brake control activity to what the module reports for actuator/solenoid status. If the tool supports it, run the ABS actuator “active test” for solenoids and note whether the left rear increasing pressure solenoid responds differently than other channels. If the tool cannot isolate that solenoid, continue with circuit testing at the connector.
6. Key off and isolate the suspect circuit using Toyota service information for the correct terminal identification. Check the solenoid coil resistance at the actuator connector pins for the left rear increasing pressure solenoid channel, and compare it to the other similar solenoid channels in the same actuator. A large mismatch points to an internal coil or internal connection problem, not a vehicle harness problem.
7. Check the harness side for shorts to ground and shorts to power with the actuator connector disconnected. Measure resistance from the control wire to chassis ground and to battery positive feed paths, and wiggle the harness during the test. Intermittent insulation faults often show up only when you move the harness near brackets or body seams.
8. Verify circuit integrity end-to-end between the actuator connector and the ABS/VSC/TRC module connector, if the design uses external module-to-actuator wiring on your Toyota platform. Perform a continuity test, then repeat it as a loaded test using a fused test light or a known load to expose high resistance. Do not rely on continuity alone, because a few strands can pass continuity and still fail under current.
9. If your scan tool supports it, command the solenoid active test and measure driver behavior at the control circuit with a DMM or scope. You should see the module switch the circuit in a controlled way, not a steady stuck-high or stuck-low condition. Use a scan tool snapshot to capture live data during the active test, because freeze frame only shows the moment the DTC set and not the entire test event.
10. After repairs, clear DTCs and perform a verification drive and/or active test sequence to confirm the fix. Recheck for pending versus confirmed status, because some monitors may set a pending fault first and confirm on a second trip. Make sure the ABS/VSC/TRC warning indicators stay off and the code does not reset.

Professional tip: When you suspect the actuator solenoid coil, compare it against another “increasing pressure” solenoid channel in the same unit. That comparison gives you a fast sanity check without needing OEM resistance specs. If power and ground drops look good and the harness passes loaded testing, the fault usually lives inside the actuator electronics or solenoid coil.

Possible Fixes

• Repair the solenoid control circuit wiring: Fix opens, shorts, or chafing, then secure the harness to prevent repeat damage.
• Restore connector integrity: Clean corrosion, correct pin fit, and replace damaged terminals at the actuator or module connector as needed.
• Correct ABS actuator power/ground faults: Repair high-resistance grounds, weak relay feeds, or poor fuse connections proven by voltage-drop testing.
• Replace the hydraulic brake actuator assembly only after circuit proof: Replace the unit when tests confirm an internal solenoid coil or internal driver fault and the external wiring checks good.
• Initialize/calibrate if required by Toyota service information: Perform any post-repair routines the scan tool prompts for, then confirm no DTC returns.

Can I Still Drive With C1355?

You can usually drive a Toyota C-HR with C1355, but you must treat it as an active brake control fault. The ABS/VSC/TRC module logs this code when it sees an electrical or functional problem in the increasing pressure solenoid circuit for the left rear hydraulic channel. When that happens, Toyota often disables ABS, traction control, and stability control. Base hydraulic braking typically remains, but the vehicle may not control wheel slip in hard stops. Expect longer stopping distances on loose or wet roads. Avoid towing, aggressive driving, and steep downhill braking until you fix it. If the brake warning lights stay on, the pedal feel changes, or braking pulls, stop driving and diagnose it now.

How Serious Is This Code?

C1355 ranges from “inconvenience” to “safety relevant,” depending on when it sets and what else the ABS/VSC/TRC module reports. If you only lose ABS/VSC/TRC and the pedal feels normal, you can often limp the Toyota C-HR to a shop under careful driving. Risk climbs fast on rain, gravel, or emergency braking because wheel lock control may not work. If you see additional hydraulic or pump-related codes, treat it as high priority. The same applies if the code returns immediately after clearing, since that points to a hard electrical fault. A solenoid circuit problem can also mask low voltage or poor grounds, so confirm power and ground integrity before you blame the actuator.

Common Misdiagnoses

Technicians often replace the ABS actuator assembly too early because the code text names a solenoid. The module message only flags a suspected trouble area, not a failed part. Many misses come from skipping connector inspection at the actuator, where moisture or terminal tension causes intermittent opens. Others ignore battery voltage and chassis grounds, which can trigger solenoid circuit codes during cranking or under load. Another common error involves testing resistance with the connector plugged in, which backfeeds the module and corrupts readings. Finally, some shops chase a wheel speed sensor because ABS lights appear, but C1355 points to hydraulic control, not speed input. Verify wiring, power, ground, and command response first.

Most Likely Fix

The most frequent confirmed repair direction for C1355 on Toyota platforms involves repairing the ABS actuator/solenoid harness or its connectors, then retesting with an active command. Focus on the actuator connector for corrosion, spread pins, and water intrusion. Perform a load-capable power and ground check at the ABS/VSC/TRC module before condemning components. If wiring checks good and the scan tool cannot command or the channel fails functional tests, the next likely direction is an ABS actuator assembly fault affecting the left rear increasing pressure solenoid circuit. Treat that conclusion as provisional until you confirm command, feedback, and circuit integrity with service information.

Repair Costs

Repair cost depends on whether the fault is wiring, a solenoid, a valve body component, or internal transmission diagnosis. Confirm the root cause with scan data before committing to a repair.

Last updated: April 9, 2026