Cummins diesel repair Chico CA. Ram 2500/3500 5.9L and 6.7L. EGR, DPF, DEF, CP4, glow plugs, dowel pins. Written diagnosis. (530) 826-4275.
Ram 2500/3500 Cummins specialist in Chico. 5.9L 12v and 24v, 6.7L. EGR cooler failure, DPF/DEF system, CP4.2 fuel pump, dowel pin failure, injector diagnosis. Written estimate before any work.
Tedious Auto Repair in Chico services Ram 2500/3500 Cummins diesels — 5.9L (12v and 24v) and 6.7L. Common issues: EGR cooler failure, DPF/DEF faults, CP4.2 high-pressure fuel pump failure, injector problems, dowel pin failure (24v 5.9L), and glow plug/grid heater service. Diagnosis before any repair. Written estimate. By Buddy Rausch, Owner · Reviewed May 20, 2026
The most notorious Cummins failure. The 1998.5–2002 5.9L 24-valve uses two dowel pins to locate the gear housing to the block. These pins back out over time, causing the gear housing to shift and the camshaft position sensor to misread — leading to a no-start condition or sudden stall. Left unaddressed, the housing can crack and destroy the front of the engine. Early symptoms: intermittent stall, hard restart, timing-related codes. Fix: machine the block, install larger oversized pins. Diagnosis required before condemning injection pump.
2019+ Ram 6.7L uses a Bosch CP4.2 high-pressure fuel pump that can catastrophically fail and send metal debris throughout the entire high-pressure fuel system — injectors, rails, and return lines. Failure often caused by fuel quality issues or water contamination. When the CP4.2 fails, the entire high-pressure fuel system must be flushed and injectors replaced. Catastrophic failure repair can exceed $10,000. Fuel filter replacement every 15,000 miles is critical prevention.
The 6.7L EGR cooler is prone to internal cracking — coolant leaks into the exhaust stream. Symptoms: white smoke from exhaust, sweet smell, coolant loss with no external leak, bubbling coolant reservoir. HC combustion test confirms coolant in exhaust. EGR cooler replacement is the fix — not a head gasket job, though symptoms are similar.
DPF regen failures from short-trip driving (common on Chico farm/ranch trucks used mostly around town). DEF quality faults from contaminated fluid or frozen DEF in Chico's occasional freezing nights. NOx sensor failure triggering limp mode. We diagnose the specific fault code and component — not assume DPF replacement.
5.9L uses a grid heater (intake manifold heater) rather than individual glow plugs. 6.7L uses glow plugs. Both cause hard cold starts, white smoke, and rough cold idle when failed. Chico's winter mornings (35–40°F) stress both systems. Tested with a current clamp — draw test confirms function without removal.
5.9L: 15W-40 CK-4 API rated. 6.7L: 15W-40 CK-4 or 0W-40 per application. Every 5,000–7,500 miles in Chico's heat. Fuel filter replacement every 15,000 miles — critical for CP4.2 protection. From $169.99.
5.9L 12-valve (1989–1998), 5.9L 24-valve (1998.5–2007), and 6.7L (2007.5–present). All in Ram 2500/3500 trucks. Common issues include dowel pin failure (24v), EGR cooler failure (6.7L), CP4.2 fuel pump (2019+), and DPF/DEF system faults.
The 24-valve 5.9L (1998.5–2007) has two dowel pins that locate the front gear housing to the block. These pins can back out, causing the housing to shift and triggering intermittent stalls, hard restarts, and timing codes. Left unaddressed, the housing cracks and destroys the engine front. Fix requires machining and oversized pin installation.
White smoke from the exhaust, sweet smell, coolant loss with no external leak visible, and bubbling in the coolant reservoir are the main signs. An HC combustion gas test confirms coolant entering the exhaust stream — same symptoms as a head gasket failure, but different repair.
5.9L: 15W-40 API CK-4. 6.7L: 15W-40 CK-4 or 0W-40 depending on application year. Never use non-CK-4 rated oil in a late-model Cummins. Fuel filter every 15,000 miles — critical for preventing CP4.2 contamination damage.
We diagnose the fault first — many DPF codes are actually NOx sensor failures, DEF quality faults, or regeneration cycle issues, not a failed filter. We identify the actual failed component before recommending replacement. DPF replacement is a last resort after all other causes are ruled out.
Written estimate before any work · ASE-Certified
📍 2695 CA-32, Chico, CA 95973 · Open Mon–Fri 7AM–6PM · Sat 8AM–5PM · Sun 9AM–5PM · Open 7 Days
2695 CA-32, Chico · (530) 826-4275 · Cummins · Duramax · PowerStroke
Buddy Rausch founded Tedious Auto Repair in Chico, CA in 2007 and has been serving Butte County for 18+ years. Buddy oversees shop standards and quality control. All content on this page reflects real procedures, OEM specifications, and cases seen in the shop. About Buddy Rausch, ASE-Certified →
Buddy Rausch founded Tedious Auto Repair in Chico, CA in 2007. ASE-Certified. 18+ years serving Butte County. About Buddy Rausch