Mercedes-Benz bulletin LI20.00-P-080222

Complaint Customer states that the yellow "Coolant" message is populated in the instrument cluster. The following DTC is found stored in the PTCU: P2B2A7A ‑ The speed of the 'Coolant pump' component part is too high. A leak or defective seal was detected Notes on fault code:The fault code concerns the right rear 15 W pump on the side of the transmission (M43/6, Figure 1, position C). The fault code concerning the speed that is too high is set because of air in the system (emergency dry run function) IMPORTANT: For model year 2024 and newer vehicles pump PN's A0005009100 and A0005008900 are the correct pumps Cause Air in the low‑temperature coolant circuit Remedy PLEASE READ ALL THE BELOW STEPS AND FOLLOW THEM IN ORDER. Step 1: With the engine cold, use XENTRY Diagnosis to activate the two pumps at the passenger front. As they are running, remove the cap from the low temp cooling circuit reservoir and observe the coolant. • If it overflows the reservoir, or blows out upon removal of the cap there is a restriction somewhere in the coolant lines. • This can take the form of a physical restriction inside of one of the lines or pumps or a damaged or kinked hardline or rubber hose. • Activate each pump in succession and listen to it using a stethoscope or by placing an ear to a screwdriver or other implement placed on the pump • Compare the sound and feel of each pump. An improperly functioning, bled, or faulty pump will make a very distinct churning noise. The pumps should be near silent and should not vibrate or heat up. • If you find a pump that is making more noise than the others it is most likely pulling in air from somewhere or is encountering a restriction (refer to the first point in this section) • If nothing of note is found, proceed to step 2. Step 2: Disassemble underfloor paneling and wheel well interior trim at front right to gain access to the two low temperature pumps. Take note of or photograph the part number of the pump holder, along with the production date. Step 3: For model year 2020‑2023 only, check the installation position of the pumps at the front right of the low‑temperature circuit (Fig. 1). Below are the correct specified part numbers at each location for these model years: • Outer: A 000 500 5500 (Fig. 1, position A) • Inner: A 000 500 3800 (Fig. 1; position B) • If installation position is NOK, continue to step 4 •

Owners of the 18 model years this bulletin names have filed 832 complaints with NHTSA since 2015. 171 of them name Engine — the same broad component group this bulletin is filed under. NHTSA groups complaints coarsely, so that means the same area of the vehicle, not necessarily the same fault.