Turbo diesel engines have advanced turbocharger and emissions systems, tuned to cleanly burn diesel fuel while taking advantage of the high torque and fuel efficiency benefits of diesel combustion. As such, modern diesel motors are equipped with extensive engine and emissions monitoring systems. This makes troubleshooting most power train problems on your turbo diesel as easy as plugging in an ECU code reader. Alternatively, there are multiple ways to troubleshoot common issues that may not trigger a "check engine" error code.
Plug an ECU error code reader into the ECU access port to troubleshoot problems that trigger the "check engine" light. Generally, the ECU access port is located on the interior centre console, above the driver side foot well. Plugging an error code reader into the access port will provide the malfunction code number as well as a brief description of the problem and parts affected. If you don't own an ECU error code reader, try taking your vehicle to a certified dealer or auto service store, as they generally offer free "check engine" code diagnosis.
Examine the turbocharger flange, as well as various turbo line connections, for signs of oil build-up. This can indicate an overly rich fuel mixture programmed into the ECU. Take your vehicle to a dealer or mechanic to have the fuel tuning or turbo boost pressure adjusted to produce a proper air-to-fuel ratio. Other signs of an overly rich tune on your diesel is excessive black smoke coming from the exhaust while accelerating.
Examine the turbo system vacuum lines and connections for any unsecured or damaged lines. Since the vacuum lines are made of rubber, they are prone to breaking down due to the high heat produced by turbocharged diesel engines, especially on high-mileage vehicles. Also, boost pressure spikes can pop the lines off of their connections. These malfunctions lead to vacuum leaks, which can cause various air-metering and emissions issues on your turbo diesel. Secure any disconnected vacuum lines, and replace damaged lines with new units. You can buy universal vacuum lines from most auto parts retailers. Simply cut them to the proper length and connect them in place of the damaged stock units.
Listen for signs of turbocharger bearing failure while accelerating the engine. Common audible signs include excessive turbo whine, as well as inconsistent turbo spool. In more extreme cases, damaged turbo bearings may produce metallic grinding noises when the turbocharger spools. Malfunctioning turbochargers need to be either rebuilt or replaced for continued engine performance and efficiency.