GLC63 AMG 2019 (M177) - Lambda 1.08 at idle - ITV/CT failure - normal behavior?
Thread Starter
Newbie
Joined: Mar 2026
Posts: 1
Likes: 0
GLC 63S AMG
GLC63 AMG 2019 (M177) - Lambda 1.08 at idle - ITV/CT failure - normal behavior?
Hi everyone,
I own a 2019 Mercedes-AMG GLC 63S 4MATIC+ (X253, M177 V8 4.0L biturbo, 510hp), registered in Andorra.
My vehicle has been failing the mandatory technical inspection (ITV) due to a lambda value of approximately 1.08–1.10 measured at idle.
The threshold applied here is the generic European default of 0.97–1.03.
Here is the situation:
- No fault codes (checked with XENTRY at Mercedes dealer)
- No air leaks found (intake, exhaust, turbo hoses all checked)
- No mechanical issues identified
- Injection system cleaned, intake system cleaned
- Engine runs perfectly, no symptoms whatsoever
- Mercedes Andorra spent 6+ weeks on the car and found nothing wrong
My question is: has anyone with a GLC63S, C63S or any M177-powered vehicle ever had their lambda measured during a technical inspection (TÜV, CT, ITV)? What was your lambda value at idle?
I'm trying to determine if 1.08 at idle is within the normal operating range of this engine by design, or if there is a genuine issue that has not been identified yet.
Any experience or data from other M177 owners would be extremely helpful.
Thanks in advance.
I own a 2019 Mercedes-AMG GLC 63S 4MATIC+ (X253, M177 V8 4.0L biturbo, 510hp), registered in Andorra.
My vehicle has been failing the mandatory technical inspection (ITV) due to a lambda value of approximately 1.08–1.10 measured at idle.
The threshold applied here is the generic European default of 0.97–1.03.
Here is the situation:
- No fault codes (checked with XENTRY at Mercedes dealer)
- No air leaks found (intake, exhaust, turbo hoses all checked)
- No mechanical issues identified
- Injection system cleaned, intake system cleaned
- Engine runs perfectly, no symptoms whatsoever
- Mercedes Andorra spent 6+ weeks on the car and found nothing wrong
My question is: has anyone with a GLC63S, C63S or any M177-powered vehicle ever had their lambda measured during a technical inspection (TÜV, CT, ITV)? What was your lambda value at idle?
I'm trying to determine if 1.08 at idle is within the normal operating range of this engine by design, or if there is a genuine issue that has not been identified yet.
Any experience or data from other M177 owners would be extremely helpful.
Thanks in advance.
