2018 Cadillac XT5 Engine Problems

Check engine light sensor came on in mid-May which is the result of a faulty thermostat, also triggering a "Steering Assist is Reduced" message on the dashboard which I consider to be a safety issue. This is a known and common problem for this make, year and model and the cost to fix the problem is very expensive. This issue has been reported by many Cadillac owners on their forum. My mechanic confirmed the problem with the thermostat caused the steering assist is reduced message, along with the air conditioning malfunctioning.

NHTSA ID

11740245

Incident

May 15, 2026

While driving at highway speeds, I needed to accelerate hard in order to pass another vehicle and while accelerating there was a downshift and increase in RPM. After passing, the RPM remained high even after I took foot off accelerator and it seemed the transmission did not shift back out of lower gear, keeping the car traveling at a high rate of speed, endangering myself and other traffic. Applying the brakes would not cause the engine to slow down and the engine kept working hard and traveling fast, causing strain on the brakes to slow down. I pulled over and initially shifted to neutral, but the engine was still revving high (4000 rpm observed). Then I placed the car in park which did not change the high RPM. Then I shut off engine and let it rest. Then I turned auto back on and all was normal. The problem has not yet been reported to dealer but will occur in coming days. There were no prior symptoms, problems, or warning lights on dash display prior to this occurring.

NHTSA ID

11727656

Incident

Mar 28, 2026

To Whom It May Concern,I am writing to formally report a safety concern involving my 2018 Cadillac XT5, VIN [XXX] . Recently, my vehicle displayed a “Steering Assist Reduced” message on the dashboard while driving. This warning significantly increases the physical effort required to steer the vehicle, especially at low speeds, and I believe it presents a genuine safety hazard.Upon taking the vehicle to an authorized Cadillac dealership, I was informed that the vehicle had stored diagnostic trouble code P0128 (Engine Coolant Temperature Below Thermostat Regulating Temperature). The dealer explained that a malfunctioning thermostat caused the steering assist reduction message to appear. However, at no point did the vehicle illuminate a Check Engine Light, despite the presence of an emissions‑related fault code.I am concerned for several reasons:A critical engine fault (P0128) did not trigger a Check Engine Light, leaving me unaware of any underlying issue. The vehicle reduced power steering assist as a result of an unrelated thermostat malfunction, creating a sudden and unexpected increase in steering effort. This behavior poses a safety risk, particularly in situations requiring quick steering response or low‑speed maneuvering.Cadillac has issued Service Bulletin 17NA158, which acknowledges that thermostat or coolant‑temperature‑related issues can trigger steering assist warnings. This suggests the manufacturer is aware of the problem, yet no recall or corrective action has been issued.Given that steering assist reduction directly affects vehicle control, I believe this issue warrants investigation. A driver should not lose steering assist because of a thermostat fault, nor should a vehicle fail to illuminate a Check Engine Light when a diagnostic code is present.I respectfully request that NHTSA review this matter to determine whether a safety‑related defect exists in the 2018 Cadillac XT5 and similar GM vehicles. Sumitting this for my mother. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOI

NHTSA ID

11712970

Incident

Jan 19, 2026

The contact owns a 2018 Cadillac XT5. The contact stated that while driving at an undisclosed speed, the vehicle inadvertently lost motive power. The contact was able to coast to the shoulder of the roadway, where the vehicle failed to restart. While attempting to restart the vehicle, the vehicle required several attempts before restarting. After the vehicle was restarted, the vehicle returned to normal functionality, but the failure became a regular occurrence, prompting the contact to discontinue driving the vehicle. No warning lights were illuminated. The vehicle was taken to an independent mechanic, who was unable to determine the cause of the failure. The vehicle was not repaired. The manufacturer was notified of the failure but provided no assistance. The contact was advised to take the vehicle to the dealer for assistance. The failure mileage was 40,000.

NHTSA ID

11696390

Incident

Oct 29, 2025

Mileage

40,000 mi

Engine thermostat defective, which causes the computer to speed up radiator fans, and causes temperature gauge to read zero. Dealer replaced under warranty at 68,000 miles and same problem reoccurred at 90,000 miles. Common problem on Cadillac XT5’s (all years)

NHTSA ID

11658849

Incident

Feb 21, 2022

The contact owns a 2018 Cadillac XT5. The contact stated that while driving at an undisclosed speed, the vehicle stalled with the check engine warning light illuminated. The vehicle was towed to the dealer where it was diagnosed that the engine had failed and needed to be replaced. The vehicle was not repaired. The manufacturer was not made aware of the failure. The approximate failure mileage was 86,000.

NHTSA ID

11650503

Incident

Mar 25, 2025

Mileage

86,000 mi

I received a Steering Assist is Reduced message and the cooling fan ramped up to full speed. In contacting Cadillac, it seems that it is a below temperature error for the thermostat. Unsure what the thermostat has to do with steering. Also in researching this, this is a wide spread issue and needs to be a recall. My XT5 has 48000 miles on it and the powertrain warranty expired 3 months ago. I believe this should be a recall and should be repaired by the manufacture as it could cause a safety issue while driving.

NHTSA ID

11621891

Incident

Oct 25, 2024

The coolant thermostat was broken and gave two check engine codes P0128 and P0128P. AC was not functioning when the thermostat was not working, which can be dangerous in summer. It is also a very common problem with Cadillac XT5 and GMC Acadia.

NHTSA ID

11615623

Incident

Sep 14, 2024

I was driving on the freeway, came to a stop as traffic increased, then the car shut off m. I had no power, could not get out of the vehicle, no hazards, no tail lights, nothing. I had a complete panic attack, I thought I was going to die. I called OnStar from my cell, they could even locate me. After 30 mins, calling 911, texting the representative from the dealership in which I purchased the car, it turned back on. Either the car was shut off with a signal or there is a serious hazardous issue that needs to be addressed.

NHTSA ID

11555562

Incident

Nov 16, 2023

When driving the car on Jul 20, the check engine light came on. It went off upon arriving home. We had it checked at our local NAPA Auto Care and they did an Electronic Engine Control Test. The garage did not clear Trouble Codes and advised us to take the car to a dealer. Upon driving the car on Jul 30, the check engine light came on once again. In May 2020, when we had our car in for service, at Sutliff, in State College, PA, they took care of the Engine Control, software issue. This dealer is no longer open so we started taking our car to Blaise Alexander in Altoona, PA We, also, have had several incidents with the Parking Brake not releasing. We took the car to Blaise Alexander, in Altoona, on 3-14-23, and they said that the software showed no problem with the Parking Brake. They advised me to call a tow truck and have it towed into their garage the next time it happened. There is a Cadillac Dealer in Ebensburg, PA which is approx 30 miles away. We are in a dilemma as to have it towed there or have it towed to the GM Dealer in Altoona, PA which is approx 16 miles away. Our car has 50, 813 miles on it. I will have it towed either to the Cadillac dealer or the GM dealer.

NHTSA ID

11535612

Incident

Jul 20, 2023

The contact owns a 2018 Cadillac XT5. The contact stated that after coming to a complete stop, the vehicle lost motive power. After restarting the vehicle, the vehicle would operate as needed. The failure occurred on multiple occasions. The cause of the failure was not yet determined. The local dealer and manufacturer were not yet notified of the failure. The failure mileage was 40,000.

NHTSA ID

11487175

Incident

Sep 1, 2021

Mileage

40,000 mi

Driving down the road and my 2018 Cadillac XT5 started on fire for no reason and no engine lights came on. I loss all driving control power steering in the matter of seconds and was trapped in the car waiting for cars to clear so I can run out. The car is with my insurance company the car is now a total loss and I don't think they will investigate. I called GM to make a complaint. The fireman said he had just put a fire out on the same car a week ago. I found out that we have 2 more cars in the Macomb county MI area that caught on fire in the last 3 months same type of car.

NHTSA ID

11466228

Incident

May 6, 2022

The contact owns a 2018 Cadillac XT5. The contact stated while driving at various speeds, the vehicle stalled. The contact stated all of the warning lights were illuminated on the control panel. The vehicle was taken to the local dealer on three different occasions where it was diagnosed with nothing needing to be replaced. The vehicle was not repaired. The manufacturer had not been informed of the failure. The failure mileage was approximately 80,264. Consumer stated vehicle completely shuts off and on without no codes or error messages.

NHTSA ID

11422217

Incident

Jun 15, 2020

Mileage

80,264 mi

EACH TIME THE CAR IS DRIVEN THE OIL % DROPS BY AT LEAST 1-2 % POINTS. SINCE SEPT 2019 THE OIL READING DROPPED TO 29%. THE DEALER CHANGED THE OIL FILTER AND SAID THE CAR WAS PERFECT. I HAVE SINCE LEARNED THAT THIS VEHICLE HAS AN OPEN RECALL. THERE IS AN OPEN RECALL ON 2018 XT5, N192266190 - ENGINE CONTROL SOFTWARE ISSUE THAT DOES NOT APPEAR ON THE CADILLAC SITE. I WAS NOT NOTIFIED.

NHTSA ID

11300250

Incident

Sep 11, 2019

TL* THE CONTACT OWNS A 2018 CADILLAC XT5. THE CONTACT STATED THAT THE FUEL SAFETY INDICATOR ILLUMINATED. THE VEHICLE WAS SERVICED FIVE TIMES, BUT THE FUEL SAFETY INDICATOR ILLUMINATED EVERY TIME THE VEHICLE WAS REPAIRED. THE VEHICLE WAS TAKEN TO TAYLOR CADILLAC (6100 CENTRAL AVE, TOLEDO, OH 43615, (419) 842-8800) WHERE A NEW EVAP PURGE VALVE WAS INSTALLED. SHORTLY AFTERWARDS, THE FUEL INJECTORS WERE REPLACED AND NEW ENGINE BANKS WERE INSTALLED. A FEW MONTHS AGO, THE FUEL SAFETY WARNING INDICATOR ILLUMINATED AGAIN. THE MANUFACTURER WAS MADE AWARE OF THE FAILURES AND A TECHNICIAN FROM THE MANUFACTURER WAS ASSIGNED TO INSPECT THE VEHICLE. THE FAILURE MILEAGE WAS 10,650.

NHTSA ID

11160915

Incident

Jul 11, 2018

Mileage

10,650 mi