U0420 on 2015-2019 Chevrolet Colorado: Power Steering Fault Causes & Fixes

What's Unique About the 2015-2019 Chevrolet COLORADO

The 2015-2019 Colorado and its sibling, the GMC Canyon, use an electric power steering (EPS) system known for communication faults. Numerous owner complaints and a recall for the 2015 model year (GM #15595) point to issues with poor electrical connections and internal component failures within the steering gear assembly. GM also issued Special Coverage N182182190, extending the warranty on this part for some 2015-2016 models to 10 years/150,000 miles, further acknowledging the defect. 🎬 Watch: A breakdown of common Colorado recalls and steering complaints. Consequently, a U0420 code on this truck is very frequently tied to a physical hardware problem in the steering system itself.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Sudden loss of power steering assist
• Steering feels very heavy or difficult to turn
• "Service Power Steering" message on the driver information center
• "Service StabiliTrak" message on the driver information center.
• "Service Trailer Brake" message on the driver information center.
• Power steering may return to normal after restarting the vehicle, but the problem is typically intermittent and gets worse over time, often being more frequent in warmer weather.

Most Likely Causes

1. Failing Electric Steering Gear Assembly 🔴 High Probability A recall for 2015 models (GM #15595) and a Special Coverage program for 2015-16 models (N182182190) were issued for poor electrical connections and torque sensor failures within the steering gear assembly. Numerous owner complaints for later years suggest the issue persists beyond the recalled population, with the internal torque sensor being the primary point of failure.
   How to confirm: A professional scan tool will often show accompanying codes like C0545 (Steering Wheel Torque Sensor Malfunction). Diagnosis involves ruling out wiring and power supply issues before condemning the expensive steering gear. If the torque sensor data on the scan tool is erratic or non-responsive, the rack has failed internally.
   Typical fix: Replace the entire electric steering gear assembly. This part contains the Power Steering Control Module (PSCM) and the torque sensor, which are the common failure points. The new part must be programmed to the vehicle.
   Est. part cost: $700-$1500
2. Weak or Failing Battery 🟡 Medium Probability Modern electronic systems, especially EPS, are highly sensitive to voltage. A weak battery can cause modules to receive low voltage, leading to communication errors and temporary shutdowns. This should be the first item checked due to its low cost and ease of testing.
   How to confirm: Test the battery with a digital battery tester. It should have a stable voltage above 12.4V with the engine off and maintain voltage under load. Check the charging system to ensure it's functioning correctly (typically 13.7-14.7V engine on).
   Typical fix: Replace the vehicle's battery.
   Est. part cost: $150-$300
3. Wiring or Connector Issues ⚪ Low Probability TSB #PIT5499B specifically mentions that water intrusion or corrosion at the Electronic Brake Control Module (EBCM) connector can cause a U0420 code, especially with a "Service Trailer Brake" message. Poor grounds are also a known GM issue; inspect the main ground connections (like G107 on the engine block) for looseness or corrosion.
   How to confirm: Visually inspect the wiring harnesses and connectors to the PSCM (on the steering rack) and the EBCM for corrosion, damage, or loose connections. A Reddit user noted that reseating the three large connectors on the passenger-side firewall resolved their issue. Check and clean main ground points on the frame and engine block.
   Typical fix: Clean or repair the corroded connector. Replace the damaged section of the wiring harness or the connector pigtail. Clean and tighten ground connections.
   Est. part cost: $20-$200

Rare But Worth Checking

• Software/Calibration Issue: In some cases, the PSCM may need a software update or recalibration. One owner reported a dealer fixed a U0420 code by performing a 'PSCM Setup' to relearn the torque sensor, which they described as 'rebooting the computer'. TSB 17-NA-190 also notes that U0420 can set transiently during a remote start event due to a power-moding issue, and advises that no repairs should be made if this is the suspected cause.

Diagnosis Steps

1. Check for any active safety recalls or special coverages. For 2015-2016 models, check VIN eligibility for GM Recall 15595 and Special Coverage N182182190 with a GM dealer.
2. Perform a full vehicle scan with a professional tool capable of reading manufacturer-specific codes from all modules (ECM, EBCM, PSCM, BCM). Document all codes, especially C0545.
3. Test the battery and charging system. Ensure voltage is stable and within specification (typically 12.4V+ engine off, 13.7-14.7V engine on).
4. Inspect main vehicle ground connections. Pay close attention to the grounds on the engine block (G107) and frame for looseness or corrosion.
5. Following TSB #PIT5499B, inspect the Electronic Brake Control Module (EBCM) connector for any signs of water intrusion or pin corrosion, especially if a trailer brake message is present.
6. Inspect the wiring harness and connector at the steering gear assembly itself for physical damage, chafing, or corrosion.
7. If codes like C0545 are present and wiring/power is good, the failure is highly likely internal to the steering gear assembly.
8. If no other cause is found, the final step is to replace the steering gear assembly, followed by the necessary programming and calibration procedures.

Parts You'll Likely Need

• Electric Steering Gear Assembly (OEM #84498587) — This is the most common point of failure. It is a complete assembly that typically includes the Power Steering Control Module and the problematic torque sensor. Note: This part number has been superseded by others like 84670808. Always verify the correct part number with the vehicle's VIN.
  Trusted brands: ACDelco, GM Genuine
  OEM price range: $900-$1600
  Aftermarket price range: $700-$1200
• Automotive Battery (AGM) — A weak battery can cause undervoltage conditions that trigger communication faults like U0420. It's a critical first check.
  Trusted brands: ACDelco, DieHard, Odyssey
  OEM price range: $200-$350
  Aftermarket price range: $150-$250

Related Codes That Often Appear With This One

• C0545 — This code specifically points to a Steering Wheel Torque Sensor malfunction. Since this sensor is integrated into the steering gear assembly, it is the most common companion code to U0420 when the assembly is failing.
• U0415 — This code means 'Invalid Data Received From ABS Control Module'. Because the StabiliTrak system (part of the ABS module) relies on steering data, a fault in the PSCM (U0420) can cause the ABS module to report that it's receiving bad data from other modules.
• C0460 — This code for 'Steering Position Sensor Malfunction' can also be logged alongside U0420, indicating a comprehensive failure of the steering system's internal sensors and communication.

Technical Service Bulletins (TSBs) & Recalls

• PIT5499B: Addresses U0420 when a 'Service Trailer Brake' message is present, pointing to water intrusion at the EBCM connector.
• GM Recall #15595 / NHTSA #15V595: A safety recall for 2015 models to replace the steering gear torque sensor cover due to a poor electrical connection.
• GM Special Coverage N182182190: An

Platform-Specific Known Issues

• NHTSA ODI Complaint #11665250: An owner of a 2016 Colorado reported power steering and Stabilitrak failure, with codes C0545 and U0420 indicating a steering wheel torque sensor malfunction.
• NHTSA ODI Complaint #11555162: A 2016 Colorado owner experienced random 'Service Power Steering' and 'Service Stabilitrak' errors, with a diagnostic code U0420-42 for 'INVALID DATA RECEIVED FROM POWER STEERING CONTROL MODULE-CALIBRATION NOT PROGRAMMED'.
• Owner Experience from Reddit: A 2016 Colorado owner reported intermittent power steering loss and Stabilitrak warnings. A dealer quoted ~$2,100 for a steering rack replacement, confirming it was a known issue even on models not covered by the original recall.

Mechanic-Grade Diagnostic Values

• PSCM Supply Voltage — expected: 12.2V to 14.8V with ignition on. Failure: Voltage below 12.2V can cause communication faults.
• PSCM Ground Resistance — expected: Less than 0.1 Ω. Failure: Higher resistance indicates a poor ground connection, which can cause data errors.

Hidden / Shadow Codes Worth Checking

• U0420-42: Invalid Data Received From Power Steering Control Module - Calibration Not Programmed. This specific symptom byte, noted in NHTSA complaint #11555162, indicates the PSCM has been replaced or reset but the mandatory calibration procedure has not been completed. (see via GM GDS2 or other professional scan tool capable of reading manufacturer-specific symptom bytes.)
• C0545-4B: Steering Wheel Torque Sensor Calibration Not Learned. This is a companion code that directly explains why U0420-42 might be set. It confirms that the torque sensor learn procedure, part of the PSCM setup, has failed or was not performed. (see via GM GDS2 or other professional scan tool.)
• U0420-71: Invalid Data Received - Actuator is not responding. This symptom byte points more directly to a hardware failure within the steering rack assembly itself, where the control module is sending commands but the mechanical or electrical components are not reacting as expected. (see via GM GDS2 or other professional scan tool.)

Scan Tool Commands That Help

• GM GDS2 (or equivalent J2534 tool): Power Steering Control Module Setup — This function is mandatory after replacing the steering gear assembly or PSCM. It runs automated routines including 'Power Steering Torque Sensor Learn' and learning the steering end-stops ('soft stops'). Failure to perform this setup will result in no power assist and will set codes like U0420-42 and C0545-4B.
• GM GDS2 (or equivalent J2534 tool): Power Steering Control Module Programming — This is required before the 'Setup' function when a new service part is installed. It loads the correct VIN-specific software and calibration files from GM's servers into the new module.

Wiring & Ground Locations

• PSCM Connector — On the electric power steering rack itself, located under the front of the vehicle.. This is the main connection for the module's power, ground, and CAN bus communication. It is exposed to the elements and physical damage. The original 2015 recall (#15595) was due to a poor connection within the torque sensor harness connector at this location.
• EBCM Connector — The Electronic Brake Control Module (EBCM) is located on the inside of the driver's side frame rail, roughly below the driver's seat.. TSB #PIT5499B identifies that water intrusion or corrosion at this specific connector can be a direct cause for code U0420, often accompanied by a 'Service Trailer Brake' message.
• Ground Splice Packs (SP105/SP106 - example) — On first-generation Colorados, these were located under the hood near the battery (SP105) and behind the engine airbox (SP106). While locations may differ on the second generation, these underhood ground distribution points are common failure points for various electrical issues due to corrosion.. A poor ground connection for any module on the CAN bus can introduce electrical noise and data errors, potentially leading other modules to report invalid data from the PSCM.

Real Owner Repair Stories

• ColoradoFans Forum user (2016 Chevrolet Colorado) — Intermittent loss of power steering, 'Service Power Steering' and 'Service Stabilitrak' messages on the dash. Codes U0420 and C0545 were present.
  ❌ Tried (didn't work) Checking battery, Inspecting visible wiring
  ✅ What actually fixed it The owner had the complete steering gear assembly (rack and pinion) replaced by the dealer. The problem was resolved. The dealer confirmed it was an internal failure of the torque sensor within the assembly, a known issue.

OEM Part Supersession History

• 84498587 → 84670808 — Standard part evolution, likely to improve reliability of the internal components that were failing.
  Heads up: Part 84670808 is a direct replacement for a long list of previous numbers including 22963310, 23353848, 84168691, 84344165, 84411672, 84450572, and 84494276. Always confirm fitment with VIN.

Model Year Variations Within This Range

• 2015-2022: The steering racks are NOT one-size-fits-all. Base models like the Work Truck (WT) and LT use a different steering rack than the off-road-oriented Z71 and ZR2 trims. This is due to differences in suspension geometry and ride height. Ordering the wrong part for the trim level will result in a part that does not fit or function correctly.
• 2015: The 2015 model year was subject to safety recall NHTSA #15V595 (GM #15595) specifically for a poor electrical connection at the torque sensor cover. The fix was to replace the cover assembly and apply specific greases. While later years exhibit the same failure mode, they were not part of this specific recall action.