Owner voices
“It Just Shut Down”: Five Owners on the Day Their CP4 Pump Failed
Published · 3 min read
A Bosch CP4 high-pressure pump does not usually fade away. In the complaints owners send to NHTSA, it stops the engine at speed. Here is what that is like, in the words of five owners of a Ford 6.7, a Duramax LML and a 2019-2020 Ram.
- The engine stalled, shut down or lost power52%
- Metal or contamination through the fuel system41%
Keyword-matched, the same set and the same patterns as our CP4 guide. One complaint can describe both. A count of reports, not a failure rate.
1. The steering and brakes get heavy at once
Engine immediately died with subsequent loss of power brakes and steering. Owner of a 2012 F-250 6.7, at 55 mph while turning onto a highway, 2015. NHTSA complaint 10746415
When the engine stops, the power assist for steering and brakes goes with it. Both still work, but they take far more force than you expect. aggregated
2. It takes seconds, not minutes
Suddenly, without any warning, we heard rattling, lost power, and the engine shut down. Owner of a 2012 Silverado 3500 Duramax towing a 15,500 lb fifth wheel, 2017. They put the whole event at about 2 to 3 seconds. NHTSA complaint 10966092
3. Downhill with a trailer, the engine brake goes too
As I was traveling on a downhill slope at approximately 60mph my engine abruptly died with no warning, causing an immediate loss of power steering, power brakes, and engine brake. Owner of a 2020 Ram 3500 towing a fifth wheel over 10,000 lb, 2021. NHTSA complaint 11438282
This is the case owners fear most: loaded, downhill, with the exhaust brake doing part of the work. The 2019-2020 Ram has since been recalled for exactly this pump. verified
4. If there is a warning, it is short
Engine light came on and engine went to limp mode for a few seconds then completely shut down. Owner of a 2015 Silverado 2500 Duramax at 70 mph with a trailer, 2023. The shop found a low fuel rail pressure code. NHTSA complaint 11510394
A check engine light, "reduced engine power" or a sudden loss of power on a CP4 truck is a reason to get off the road now, not at the next exit. aggregated
5. The pump takes the fuel system with it
The CP4 HP pump had failed contaminating the entire fuel system. The repair bill was ~$8,200. Owner of a 2013 F-250 6.7, 2018. NHTSA complaint 11143865
When the pump wears inside, metal travels through the rails and injectors, so the repair is rarely just a pump. In the complaints behind our CP4 guide, owners reported $7,000 to $17,000, and one 2019 Ram estimate was $20,000. aggregated
If it happens to you
- Steer and brake hard, early. Signal, use the momentum you have to reach the shoulder, and expect heavy steering and brakes.
- Do not keep cranking it. Shops advise against repeated restarts after a pump failure, which can pull more debris through the system. Have it towed. aggregated
- Check your VIN. Ram replaced the pump on 2019-2020 trucks under recall 21V-880. Ford's recalls on 2020-2022 trucks (24V-957 and 26V-158) update software; the pump stays. We found no GM recall for the LML pump. verified
Which trucks have a CP4, which years fail and what the recalls cover: CP4 pump: which diesel trucks have it.
Sources. NHTSA owner complaints database (US government public domain), the CP4 complaint set of our CP4 guide; quotes are taken from complaint narratives with capitalization normalized, and complaint numbers are given so you can read them in full. NHTSA recall records 21V-880, 24V-957 and 26V-158. Torque Index aggregates and cross-checks public information, takes no paid placement and does not provide repair or inspection services.