ios – AFNetworking 2.0 Domain = AFNetworkingErrorDomain Code = -1011“请求失败：内部服务器错误(500)

我试图将我的代码转换为AFNetworking 2.0与分类AFHTTPRequestOperationManager.这是我的代码

+ (NSAFNetwokingRequestManager *)sharedClient {
    static NSAFNetwokingRequestManager *_sharedClient = nil;

    static dispatch_once_t onceToken;
    dispatch_once(&onceToken,^{
        _sharedClient = [[self alloc] initWithBaseURL:[NSURL URLWithString:GET_CAR_BRAND]];
    });
    return _sharedClient;
}
- (instancetype)initWithBaseURL:(NSURL *)url
{
    self = [super initWithBaseURL:url];
     if (self) {
    self.responseSerializer = [AFXMLParserResponseSerializer serializer];
    self.responseSerializer.acceptableContentTypes = [NSSet setWithObject:@"application/soap+xml"];
    self.requestSerializer = [AFHTTPRequestSerializer serializer];
    [self.requestSerializer setValue:@"application/soap+xml" forHTTPHeaderField:@"Content-type"];
}

    return self;
}
- (void)requestBrandcompletion:(NSAFNetwokingRequestManagerCompletionBlock)completion {
    NSString *soapRequest=@"<?xml version="1.0" encoding="utf-8"?>n"
    "<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">n"
    "<soap:Body>n"
    " <CarBrandExt xmlns="http://www.nohausystems.nl/" />n"
    "</soap:Body>n"
    "</soap:Envelope>n";
    NSString *msgLength = [NSString stringWithFormat:@"%i",[soapRequest length]];
    [self POST:GET_CAR_BRAND parameters:Nil constructingBodyWithBlock:^(id<AFMultipartFormData> formData) {
          [formData appendPartWithHeaders:[NSDictionary dictionaryWithObjectsAndKeys:@"text/xml; charset=utf-8",@"Content-Type",msgLength,@"Content-Length",nil] body:[soapRequest dataUsingEncoding:NSUTF8StringEncoding]];
    } success:^(AFHTTPRequestOperation *operation,id responSEObject) {
        if (completion) {
            completion(YES,responSEObject);
        }
    } failure:^(AFHTTPRequestOperation *operation,NSError *error) {
        if (completion) {
            completion(NO,nil);
            NSLog(@"Unable to fetch record error %@ with user info %@.",error,error.userInfo);
        }
    }];
}

我收到这个错误Domain = AFNetworkingErrorDomain Code = -1011“请求失败：内部服务器错误(500).任何人可以告诉我我在这里做错了什么？
得到这个回应：

{ status code: 500,headers {
    "Cache-Control" = private;
    "Content-Length" = 509;
    "Content-Type" = "application/soap+xml; charset=utf-8";
    Date = "Thu,13 Mar 2014 12:59:45 GMT";
    Server = "Microsoft-IIS/7.5";
    "X-AspNet-Version" = "2.0.50727";
    "X-Powered-By" = "ASP.NET";
} }

[self POST:GET_CAR_BRAND parameters:Nil constructingBodyWithBlock:^(id<AFMultipartFormData> formData) {
          [formData appendPartWithHeaders:[NSDictionary dictionaryWithObjectsAndKeys:@"text/xml; charset=utf-8",nil] body:[soapRequest dataUsingEncoding:NSUTF8StringEncoding]];

[self POST:GET_CAR_BRAND parameters:Nil constructingBodyWithBlock:^(id<AFMultipartFormData> formData) {
          [formData appendPartWithHeaders:[NSDictionary dictionaryWithObjectsAndKeys:@"application/sopa+xml; charset=utf-8",nil] body:[soapRequest dataUsingEncoding:NSUTF8StringEncoding]];

[self.requestSerializer setValue:@"application/soap+xml; charset=utf-8" forHTTPHeaderField:@"Content-Type"];