Mileage when the problem started
Owner reports
Selected complaints filed with NHTSA by 2017 Cadillac XT5 owners, lightly cleaned up (personal details are redacted by NHTSA).
The contact owns a 2017 Cadillac XT5. The contact stated while driving approximately 40 MPH, the vehicle overheated and stalled. The power steering assist was reduced with the drive with care message displayed. The local dealer was not contacted. The vehicle was not diagnosed or repaired. The vehicle was taken to an independent mechanic who informed the contact about the thermostat failure, engine, and DTC: P0128. The manufacturer was not contacted. The approximate failure mileage 43,806.
This model Cadillac XT5 has early failures of engine cooling systems thermostats. The thermostat sticks open causing lower engine temperatures and higher emissions. The first sign you have an issue is a reduced power steering assist message on the instrument display. The engine control module stores a p0128 code as current. Continue driving the vehicle the ECM will shut off AC compressor engagement, so no AC. The next thing that happens is you lose temperature gauge. So you are now driving vehicle with reduced power steering assist, no AC and no way of knowing if the engine is overheating. This is a known issue with the refer to GM bulletin # 17-NA-158 posted May 2017. There has been a such a demand for this thermostat, that parts back orders are common. The volume of failures should be addressed as a recall including refunds to owners who have had to pay for this repair. …
Catalytic Converter on my 2017 XT5 had weld crack Oct 2025. Causing loud noise and exhaust to enter cabin of vehicle. This was the second convertor to do this. In 2023 I had to have the other catalytic convertor on this same vehicle changed out by the Sewell Cadillac dealership for the same problem. That time I only had 50,000 miles on the car so the dealership did it for free (after I found that they had to cover up to 80,000 and they acted like they didn't know that and had quoted me $2000). This time in 2025 I had 80,805 miles so I had to pay $1010 to have it replaced by an outside repair shop. The technician says since we had to have them both replaced and the car is only 8 years old, it is probably a design flaw. He told me to report it. …
The thermostat is malfunctioning. Vehicle has less than 50,000 miles. Driving vehicle and dash warning" STEERING ASSIST IS REDUCED DRIVE WITH CARE", also the temperature gauge was showing COLD and this was after driving for over 30 minutes. Contacted local dealer and was informed this is a KNOWN problem with the thermostat sticking open. If this had been in the summer the A/C would not have worked. I was informed I could bring in the vehicle to have the codes cleared and the parts would have to be ordered. Due to backlog of parts, it was unknown when the parts would be available. In searching internet there are a significant number of owners who have experienced the same issue. In consulting the mechanic, I use, I was informed this is an issue with the motor in my vehicle. The same motor is in other GMC products, and he has 3 vehicles in his shop with the same issue waiting parts.
While driving my vehicle, alert popped up on my dash stating "Steering Assist is Reduced Drive with Care" futhermore after that my Check Engine Light Turned on and my Engine Heater Stayed cold and would not warm up. Vehicle has been inspected by the Cadillac Dealer and they stated it is all due to the Sensor. However Sensor is on backorder and has taken them 3 week to get the part. They stated it is safe to drive even though all those alerts came up, since he said it appears to be stuck open, however they stated if it gets stuck in a closed state then the engine could overhead which would require having the vehicle towed in. They offer a "limited" warranty on this however since I just was past the warranty period they state you have to pay the full price. Warranty is for 85,000 miles and I am barely above it at 87675.
Our XT5 began getting 'Steering Assist Reduced' message about a year ago. It comes and goes , coming more often now. The problem is the thermostat and is a very common issue with numerous complaints here and on Cadillac forums (below). The problem is, when this issue occurs the AC stops working, and when that happens you have no windshield defrost, and that is a safety problem. Cadillac has TSB's describing this issue but refuses to cover it goodwill as we are slightly out of warranty. The repair is extensive, requiring 4.5 of time. [redacted]
ECM- engine system. Diagnostic code P26C8. Chassis Control Module Requested Malfunction Indicator Lamp Illumination. The DTC is an informational DTC. The DTC indicates an emission related DTC set in the Chassis Control Module. My service transmission message came on and would not let me go into reverse or drive. The next day the check engine light was on. This vehicle is only 34,650 miles and is a 2017. I bought it on Saturday and this happened on Wednesday!
The thermostat has malfunctioned twice in 2 years. Driving vehicle and dash warning" STEERING ASSIST IS REDUCED DRIVE WITH CARE", also the temperature gauge was showing COLD and this was after driving for over 30 minutes. Contacted local dealer and was informed this is a KNOWN problem with the thermostat sticking open. My brakes are sticking often and my car often jumps hard when i put it in reverse.
engine light comes on, brake assist service light comes on when transmission idles down at stop signs, stabilitrak service light comes on after transmission idles down after a stop. This has happened twice and I had to get it repaired.
I had P0128 Code with a warning message " Steering assist is reduced, drive with care". My local mechanic told I need a new thermostat. I have replaced my thermostat and it cost me 700 dollars out of pocket.
Engine complaints in other XT5 years
Frequently asked questions
How common are engine problems on the 2017 Cadillac XT5?
NHTSA has 24 complaints about the engine & cooling of the 2017 Cadillac XT5, 19% of the model year's 124 complaints.
Is there a recall for 2017 Cadillac XT5 engine problems?
No. NHTSA lists no engine & cooling recall for the 2017 Cadillac XT5, though it has 1 recall for other components. If the problem is widespread, a repair may still be covered by an extended warranty or a manufacturer service bulletin — ask a dealer.
At what mileage do 2017 Cadillac XT5 engine problems start?
Half of the complaints with a recorded mileage happened before about 16,000 miles, and 67% before 25,000 miles.
Source: U.S. National Highway Traffic Safety Administration (NHTSA) — owner complaints through October 20, 2026, recalls and defect investigations; fuel economy from the EPA. Complaints are unverified reports and are not proof of a defect. How we rate model years.