Vehicles affected: P11 - 12C, 12C Spider, 650S, 6508 Spider, 625C. P13 - 570S, 570S
Spider, 540C, 570GT, 600LT

Location: Engine Systems - Engine Miscellaneous
Topic: Lack of power and/or MIL light ON
Condition: Under acceleration

Diagnostic Trouble Codes: ECM:
PO29900 Boost Pressure Control Bank 1 Under Boost

PO2CBOO Boost Pressure Control Bank 2 Under Boost

P023400 Boost Pressure Control Bank 1 Over Boost

PO2CAO0 Boost Pressure Control Bank 2 Over Boost

P226100 Turbocharger Bypass Valve (Dump Valve) Bank 1 Monitor pulsations in
induction system (Dump Valve Rationality)

POOC400 Turbocharger Bypass Valve (Dump Valve) Bank 2 Monitor pulsations in
induction system (Dump Valve Rationality)

Measure

Care Point: Sports Series and 675LT vehicles only have wastegate’s controlled by
this circuit. The dump valves are controlled by an electronic actuator. This guide can
be used for these vehicles also, excluding Step 4.

System Overview

Below is a diagram (1) of the turbo control system.

a anit)

Vacuum connections & control
1 Secondary air actuators

RH Turbo 2 Dump vaive solenoid

3 Wastegate solenoid

4 Secondary air solenoids

5 Turbo dump/recirculation valve
6 Wastegate actuator

Ee Vaccum
BB Vaccum
Fl Pressure

El Pressure bleed

LH Turbo

Below is a picture (2) of the Bank 1 turbo control circuit connections for reference
purposes.

1 Dump valve

2 Pressure out
ma 3 Waste gate

>, 4 Pressure bleed

The tooling required is a vacuum/pressure tester, an example is shown below (3).

Diagnosis Guide
Step 1:

Care Point: Always check wastegate adjustment after any leak repair or component
replacement.

Ensure all the connections of turbos are secure as shown in picture (2) and with the
correct size Oetiker clamps (the dump valve pipe should be bonded on with Loctite
454). If aloose pipe is found refit correctly, clear faults and road test. If fault does
not return no further action is required.

If all the connections are secure, pressure test the turbo control circuit on each bank
even if only one bank has a DTC stored. Remove the 90 degree elbow (as shown on
image 4 ) from each turbo, pressurise each circuit in turn up to 12 psi.

At this point there are four possible results:

1, No pressure Is built up in the system - proceed to Step 3
2. Pressure builds but decays after 1 minute - proceed to Step 3

3. Pressure builds, the wastegate actuator moves and the pressure holds for more
than 1 minute - proceed to Step 2

4, Pressure builds, the wastegate actuator doesn't move and the pressure holds for
more than 1 minute - proceed to Step 6

Step 2:

If both wastegates open and the circuit holds pressure, the adjustment of the
wastegate could be incorrect. If this is the case, carry out the adjustment procedure
on SIS “Remove/install wastegate assembly - turbo charger" for the relevant model,
(ignore the steps to remove and install the waste gate actuator),

If you cannot get a wastegate adjustment into spec then you will need to replace the
wastegate actuator.
Step 3:

If one or more turbo circuits do not build any pressure, you will need to carry out the
following steps on each faulty circuit.

We now need to find the leak in the system. To do this start by removing and
blanking off the 90 deg rubber pipe on the waste-gate (2) then try to pressurise the
circuit. If it does at this point build pressure, then you have a fault with this
wastegate.

er

Step 4:

Once both wastegates have been checked and found to be ok, proceed to check the
dump valves on each circuit. Detach the 90 degree rubber pipe (3) on each dump
valve, With the pipe removed, check that the elbow pipe and dump valve are not
blocked/restricted with Loctite.

Now insert a bung into the elbow and pressurise the circuit again on each bank. If
pressure now builds then the fault is with the dump valve. To confirm the dump
valve is faulty, connect the vacuum/pressure gauge directly to the dump valve.
Set the pump to vacuum and pump up to 75Kpa, If no vacuum is generated or it
decays within a minute then the dump valve is faulty.

Step 5:
At this point if pressure does not build then the fault is with the vacuum harness.

There is another test to confirm this, detach the 90 degree vacuum harness
pressure bleed pipe elbow (4) that connects to the MAF tube, blank it off. Pressurise
the system, if it now builds pressure the vacuum circuit is confirmed as faulty.

Step 6:

If the wastegate is not moving when the system is pressurised, the wastegate is
seized. Please refer to the SIS instruction “Remove/install wastegate assembly -
turbo charger” for the relevant model and follow steps to undo the turn buckle (5),
Then check if the wastegate arm can be moved, it should move freely,
KA Updates Information

21/04/2021 - Template Update

This document is uncontrolled when printed. Before use, check the Knowledge Base

within the McLaren Retailer Portal to verify that this is the current version.